Before I list down the list of PR6 to PR 9 directories, it’s essential to understand why directory is important towards your website SEO and what criterion that constitute a SEO-friendly directory.

What is SEO-friendly directory?
SEO friendly directory means one that contains pages which are spiderable by search engine robots and can be assigned a PR (pagerank). A SEO friendly directory will help to improve your website PR should yours is listed in the directory. There’s a lengthy explanation of criterion that constitute SEO friendly directory, they can be boiled down to the following brief summary.

SEO friendly directory does not:

• Use Redirects
• Use no index, no follow tags
• Have too many links on one page
• Prevent directory pages with robots.txt
• Put listings too deep for a single category

SEO friendly directory does:

• Make the links look readable as static links
• Use plain HTML < a href > links
• Put links with meaningful anchor text
• Use Mod rewrite
• Use sitemap

The following is the lengthy list of the directories which are sorted out in descending order.

9 http://search.freefind.com .
9 http://www.boingboing.net .
9 http://www.dmoz.org .
8 http://directory.google.com .
8 http://search.com .
8 http://search.epnet.com .
8 http://search.internet.com .
8 http://www.big-boards.com .
8 http://www.bloglines.com .
8 http://www.bubl.ac.uk .
8 http://www.fastsearch.com .
8 http://www.foxsearchlight.com .
8 http://www.lii.org .
8 http://www.lii.org/pub/htdocs/home.htm .
8 http://www.mriresearch.org .
8 http://www.musicmoz.org .
8 http://www.nlsearch.com .
8 http://www.picosearch.com .
8 http://www.researchbuzz.com .
8 http://www.rssreader.nl .
8 http://www.scirus.com .
8 http://www.scriptsearch.com .
8 http://www.searchinsider.com .
8 http://www.topix.net .
8 http://www.uncoverthenet.com .
8 http://www.yahooligans.yahoo.com .
7 http://dir.search.ch .
7 http://search.earthcam.com .
7 http://search.mnogo.ru .
7 http://search.namazu.org .
7 http://uk.mobile.yahoo.com .
7 http://www.1234-find-web-designers.org .
7 http://www.1stindustrialdirectory.com .
7 http://www.2rss.com .
7 http://www.agingresearch.org .
7 http://www.allheadlinenews.com .
7 http://www.amrresearch.com .
7 http://www.ananzi.co.za .
7 http://www.art.net .
7 http://www.arthritis-research.com .
7 http://www.astronomylinks.com .
7 http://www.asylumresearch.com .
7 http://www.aussie.com.au .
7 http://www.awesomelibrary.org .
7 http://www.bioresearch.ac.uk .
7 http://www.blogcatalog.com .
7 http://www.blogcritics.org .
7 http://www.blogpulse.com .
7 http://www.bloguniverse.com .
7 http://www.botw.org .
7 http://www.cancerresearch.org .
7 http://www.cancerresearchuk.org .
7 http://www.cansearch.org .
7 http://www.capsresearch.org .
7 http://www.chemdex.org .
7 http://www.consumersearch.com .
7 http://www.crosssearch.com .
7 http://www.dmoz.com .
7 http://www.downes.ca .
7 http://www.dtsearch2.com .
7 http://www.educationindex.com .
7 http://www.elib.org .
7 http://www.emteachline.com/links .
7 http://www.envirolink.org .
7 http://www.exactseek.com .
7 http://www.familysearch.org .
7 http://www.fbresearch.org .
7 http://www.femina.com .
7 http://www.firstsearch.oclc.org .
7 http://www.fotosearch.com .
7 http://www.freehotelsearch.com .
7 http://www.freepatentsonline.com .
7 http://www.globalresearch.ca .
7 http://www.guardian.co.uk/weblog .
7 http://www.headlinespot.com .
7 http://www.hostsearch.com .
7 http://www.hsrd.research.va.gov .
7 http://www.info.gov/phone.htm .
7 http://www.jobsearch.gov.au .
7 http://www.joslinresearch.org .
7 http://www.kids4research.org .
7 http://www.libdex.com/weblogs.html .
7 http://www.lsblogs.com .
7 http://www.marketingtool.com .
7 http://www.mnogosearch.org .
7 http://www.msdssearch.com .
7 http://www.music-research.org .
7 http://www.mwsearch.com .
7 http://www.newsmob.com .
7 http://www.panopticsearch.com .
7 http://www.picsearch.com .
7 http://www.pingomatic.com .
7 http://www.pubsub.com .
7 http://www.researchamerica.org .
7 http://www.science.cancerresearchuk.org .
7 http://www.searchbiblio.com .
7 http://www.searchedu.com .
7 http://www.searchengines.com .
7 http://www.searchgov.com .
7 http://www.searchmil.com .
7 http://www.searchopolis.com .
7 http://www.searchsystems.net .
7 http://www.searchtools.com .
7 http://www.securitysearch.net .
7 http://www.sldirectory.com .
7 http://www.sportsvl.com .
7 http://www.theweblogreview.com .
7 http://www.umresearch.umd.edu .
7 http://www.weblogalot.com .
7 http://www.wine-searcher.com .
7 http://www.worksearch.gc.ca .
7 http://www.worldhot.com .
7 http://www.worldweb.com .
7 http://www1.lanic.utexas.edu .
6 http://crl.research.compaq.com .
6 http://dir.evolt.org .
6 http://directory.sootle.com .
6 http://directory.v7n.com .
6 http://lsi.research.telcordia.com .
6 http://search.bg .
6 http://search.biography.com .
6 http://search.dreamwiz.com .
6 http://search.ieice.org .
6 http://search.mrsc.org .
6 http://search.t1msn.com.mx .
6 http://search.yumyum.com .
6 http://search.yupimsn.com .
6 http://search2.msn.fr .
6 http://www.2yi.net .
6 http://www.aaa.com.au .
6 http://www.aaabooksearch.com .
6 http://www.ableseek.com .
6 http://www.accessnz.co.nz .
6 http://www.agentresearch.com .
6 http://www.agresearch.cri.nz .
6 http://www.aigam.com .
6 http://www.all-linksite.com .
6 http://www.alltopsites.info .
6 http://www.allwebscape.com .
6 http://www.americasbest.com .
6 http://www.aramis-research.ch .
6 http://www.aresearchguide.com .
6 http://www.artpromote.com .
6 http://www.artseek.com .
6 http://www.ascrocco.it .
6 http://www.asiajobsearch.org .
6 http://www.atuk.co.uk .
6 http://www.avatarsearch.com .
6 http://www.azoos.com .
6 http://www.bccresearch.com .
6 http://www.beaconpost.com .
6 http://www.best-searchengine.com .
6 http://www.bible-researcher.com .
6 http://www.bioresearchonline.com .
6 http://www.blogbits.com .
6 http://www.blogdir.com .
6 http://www.blogsweet.com .
6 http://www.bltresearch.com .
6 http://www.blurtit.com .
6 http://www.bomis.com .
6 http://www.bpchildresearch.org .
6 http://www.britishinformation.com .
6 http://www.browse8.com .
6 http://www.bulkfeeds.net .
6 http://www.business-directory-uk.co.uk .
6 http://www.businessseek.biz .
6 http://www.canadopedia.com .
6 http://www.canlinks.net .
6 http://www.capitalresearch.org .
6 http://www.carsearch.com .
6 http://www.celebhoo.com .
6 http://www.chembridgeresearch.com .
6 http://www.childsearch.org .
6 http://www.chiresearch.com .
6 http://www.christiansunite.com/allcat.shtml .
6 http://www.cinemaspot.com .
6 http://www.cinemedia.org .
6 http://www.classearch.com .
6 http://www.clickandsearch.com .
6 http://www.clickey.com .
6 http://www.comeonaussie.com .
6 http://www.compinfo-center.com .
6 http://www.consumermatch.com .
6 http://www.contentsmatter.com .
6 http://www.cooperativeresearch.org .
6 http://www.corporatelistings.net .
6 http://www.crayon.net .
6 http://www.crime-research.org .
6 http://www.cyber-find.net .
6 http://www.cybersleuth-kids.com .
6 http://www.datacommresearch.com .
6 http://www.datastoragesearch.com .
6 http://www.demographic-research.org .
6 http://www.diarist.net .
6 http://www.dirblog.com .
6 http://www.directorymarker.com .
6 http://www.directoryworld.net .
6 http://www.dirspace.com .
6 http://www.docusearch.com .
6 http://www.dtsearch.co.uk .
6 http://www.dvdpricesearch.com .
6 http://www.earthlook.com .
6 http://www.easyrss.com .
6 http://www.ecoiq.com .
6 http://www.egyptsearch.com .
6 http://www.elasmo-research.org .
6 http://www.emoblue.info .
6 http://www.energysearch.com .
6 http://www.engineersedge.com .
6 http://www.equityresearchcenter.com .
6 http://www.esearchgroup.com .
6 http://www.esperanto.se/kiosk/engindex.html .
6 http://www.euresearch.ch .
6 http://www.execsearches.com .
6 http://www.ezilon.com .
6 http://www.familyfriendlysearch.com .
6 http://www.feedsfarm.com .
6 http://www.find.co.uk .
6 http://www.findingblog.com .
6 http://www.fishresearch.org .
6 http://www.foreclosurefreesearch.com .
6 http://www.forestresearch.co.nz .
6 http://www.freewebdirectory.us .
6 http://www.friendsearch.com .
6 http://www.fybersearch.com .
6 http://www.game-research.com .
6 http://www.genecast.com .
6 http://www.gimpsy.com .
6 http://www.golfsearch.com .
6 http://www.haabaa.com .
6 http://www.hamptonresearch.com .
6 http://www.hearingresearch.org .
6 http://www.highpagerank.net .
6 http://www.hockeyresearch.com .
6 http://www.hondaresearch.com .
6 http://www.hortresearch.co.nz .
6 http://www.hotelsearch.com .
6 http://www.hyeguide.com .
6 http://www.hypography.com/links.cfm .
6 http://www.idcresearch.com .
6 http://www.imegamall.com .
6 http://www.inclusionresearch.org .
6 http://www.indiamart.com .
6 http://www.info-listings.com .
6 http://www.intel-research.net .
6 http://www.iozoo.com .
6 http://www.island-search.com .
6 http://www.itravelnet.com .
6 http://www.javascriptsearch.com .
6 http://www.jayde.com .
6 http://www.jdgsearch.com .
6 http://www.jobsearch.co.uk .
6 http://www.job-search-engine.com .
6 http://www.jobsearchlink.com .
6 http://www.joeant.com .
6 http://www.jrnlappliedresearch.com .
6 http://www.kidsites.org .
6 http://www.kmax.ws/bloglinks.htm .
6 http://www.laborresearch.org .
6 http://www.landcareresearch.co.nz .
6 http://www.lawresearch.com .
6 http://www.lawresearchservices.com .
6 http://www.lawyershop.ca .
6 http://www.lessonplansearch.com .
6 http://www.lightsearch.com .
6 http://www.linkcentre.com .
6 http://www.linkwith.us .
6 http://www.lionresearch.org .
6 http://www.localpin.com .
6 http://www.lookseek.com .
6 http://www.mainesearch.net .
6 http://www.maven.co.il .
6 http://www.mediaresearch.org .
6 http://www.medic8.com .
6 http://www.medsearch.com .
6 http://www.memigo.com .
6 http://www.mirago.co.uk .
6 http://www.myjobsearch.com .
6 http://www.newcastle.research.ec.org .
6 http://www.newsknowledge.com .
6 http://www.nmsitesearch.com .
6 http://www.nonprofitresearch.org .
6 http://www.ntcresearch.org .
6 http://www.nzs.com .
6 http://www.nzsearch.co.nz .
6 http://www.octopedia.com .
6 http://www.organic-research.com .
6 http://www.pacificresearch.org .
6 http://www.patient.co.uk/topics.asp .
6 http://www.personalityresearch.org .
6 http://www.perso-search.com .
6 http://www.philanthropysearch.com .
6 http://www.pingoat.com .
6 http://www.pinonsale-webdirectory.com .
6 http://www.planetsearch.com .
6 http://www.pocketsearchengine.com .
6 http://www.pointresearch.com .
6 http://www.policyresearch.gc.ca .
6 http://www.porthardybc.ca .
6 http://www.prosearch.com .
6 http://www.qualitative-research.net .
6 http://www.railjobsearch.com .
6 http://www.rb-marketresearch.com .
6 http://www.relmaxtop.com .
6 http://www.researchandmarkets.com .
6 http://www.researchmag.com .
6 http://www.researchpubs.com .
6 http://www.rlrouse.com .
6 http://www.romance-search.com .
6 http://www.rw-designer.com/directory .
6 http://www.sageresearch.com .
6 http://www.schaeffersresearch.com .
6 http://www.scienceport.org .
6 http://www.search4dinosaurs.com .
6 http://www.search4rss.com .
6 http://www.search66.com .
6 http://www.searchability.com .
6 http://www.search-associates.com .
6 http://www.searchbc.com .
6 http://www.searchbliss.com .
6 http://www.searchboston.com .
6 http://www.searchbutton.com .
6 http://www.searchcode.de .
6 http://www.searchcodes.de .
6 http://www.searchdesk.com .
6 http://www.searchebooks.com .
6 http://www.searchengineworkshops.com .
6 http://www.searchengineworld.com .
6 http://www.searchenginez.com .
6 http://www.searcheurope.com .
6 http://www.searchindia.com .
6 http://www.search-institute.org .
6 http://www.searchlightmagazine.com .
6 http://www.searchlores.org .
6 http://www.searchmalta.com .
6 http://www.searchnz.co.nz .
6 http://www.searchspace.com .
6 http://www.searchthe.net .
6 http://www.searchwise.net .
6 http://www.searchwiz.com .
6 http://www.seedirectory.com .
6 http://www.self-directed-search.com .
6 http://www.seniorssearch.com .
6 http://www.seocompany.ca .
6 http://www.serverfiles.com .
6 http://www.shopping-search.jp .
6 http://www.sitepronews.com .
6 http://www.skaffe.com .
6 http://www.socialworksearch.com .
6 http://www.spamlinks.net .
6 http://www.spike2000.com .
6 http://www.spurl.net .
6 http://www.stanleyresearch.org .
6 http://www.stemcellresearch.org .
6 http://www.storagesearch.com .
6 http://www.surrey-research-park.com .
6 http://www.thefreeguide.com .
6 http://www.thelanka.com .
6 http://www.top100travelsites.com .
6 http://www.travel-quest.co.uk .
6 http://www.tripspot.com .
6 http://www.truthlaidbear.com .
6 http://www.tuttoperinternet.it .
6 http://www.tygo.com/dir .
6 http://www.ukdirectory.co.uk .
6 http://www.umdum.com .
6 http://www.urlz.net .
6 http://www.verdictsearch.com .
6 http://www.vxbox.com .
6 http://www.walkerresearch.com .
6 http://www.wbresearch.com .
6 http://www.webbresearch.com .
6 http://www.webwizguide.com .
6 http://www.webworldindex.com .
6 http://www.wizdirectory.com .
6 http://www.worldsiteindex.com .
6 http://www.wowdirectory.com .
6 http://www.wxresearch.com .
6 http://www.yourwebloghere.com .
6 http://www.yusearch.com .
6 http://www.zensearch.com .
6 http://www.zepti.net .
6 http://www.zeroland.co.nz .
6 http://www.zunchdirectory.com .

Please bear in mind that the PR associated to the directories might not reflect the recent PageRank update. I hope the list will ease off the hassle in finding good directory for your websites.

[credit to Moneybookersclubvia DigitalPoint]

Updates: Rosie over at SEO reloaded has a complete list of directories. It’s worth to take a look at the page