There's a pretty large list at wikipedia too http://en.wikipedia.org/wiki/List_of_social_networking_websites
this is a list of social bookmarking site http://www.socialposter.com/ http://www.wmtips.com/SEO/list-high-social-bookmarking-sites-668.htm
a long time back, I had put the list http://social.nbridges.com/ still working though little outdated...
http://www.facebook.com http://www.reddit.com/ http://www.skelbimai.co.uk http://www.stumbleupon.com/ http://www.squidoo.com/why http://www.lensroll.com/ http://del.icio.us/ http://www.digg.com/ http://www.twitter.com/ http://www.blinklist.com/ http://www.gather.com/inviteLanding.jsp?parentMemberId=257153&tc=14 http://ma.gnolia.com/ http://www.plugim.com/ http://blogmarks.net/ http://www.citeulike.org/ http://www.furl.net/learnMore.jsp http://www.newsvine.com/ http://www.technorati.com/ http://www.netscape.com/ http://www.rawsugar.com/ http://www.simpy.com/ http://www.spurl.net/ http://myweb.yahoo.com/ http://www.zlitt.com/ http://www.rollyo.com/ http://www.bibsonomy.org/ http://www.blabb.com/ http://faves.com/home http://www.backflip.com/ http://aboogy.com/ http://www.a1-webmarks.com/ http://www.clipmarks.com/ http://www.connotea.org/ http://www.minddeposit.com/ http://www.livefavorites.com/ http://www.ning.com/ http://www.rojo.com/ http://www.shadows.com/ http://www.spotback.com/ http://www.reddit.com/ http://hubpages.com/_recommended/hub/howhubworks http://askville.amazon.com/ http://www.blinkbits.com/ http://bandbuzzer.com/ http://www.blinkpro.com/ http://www.bookmark-manager.com/ http://www.bookmarkbuddy.net/ http://www.blogmemes.net/ http://www.bookmarkcommando.com/ http://www.sync2it.com/ http://buddymarks.com/ http://www.bookmarkmagic.com/ http://www.bookmarktracker.com/ http://www.butterflyproject.nl/ http://www.bookmax.net/ http://www.care2.com/news http://claimid.com/ http://www.clickmarks.com/ http://www.connectedy.com/ http://de.lirio.us/ http://www.diigo.com/ http://www.easybm.com/ http://www.eigology.com/dogear http://dohat.com/ http://freelink.org/ http://frassle.rura.org/ http://www.finety.com/ http://www.complore.com/ http://www.globusport.com/ https://www.google.com/bookmarks http://www.fungow.com/ http://www.guicookies.com/ http://www.getboo.com/ http://www.humdigg.com/ http://www.dudecheckthisout.com/ http://www.hamiltontechgroup.com/ http://www.i89.us/index.php http://www.hyperlinkomatic.com/ http://www.ifaves.com/ http://ww2.ikeepbookmarks.com/Default.asp http://www.jots.com/ http://www.kmfavorites.com/ http://linkroll.com/ http://www.links2go.com/ http://www.favmark.com/ http://www.favoor.com/ http://linkagogo.com/go/Society http://linksnarf.com/ http://www.lookmarks.com/ http://www.kaboodle.com/ http://www.markaboo.com/ http://www.link2mark.com/ http://www.mobleo.net/ http://murl.com/ http://lounge.ifastnet.com/ http://www.memfrag.com/ http://waveright.homeip.net/products/FavoritesAnywhere.html http://www.myhq.com/ http://www.mybookmarks.com/ http://www.myhotlist.com/ http://www.mybookmarkmanager.com/ http://linkatopia.com/ http://www.mywebdesktop.net/ http://www.mylinkvault.com/ http://www.netvouz.com/ http://www.onlinebookmarkmanager.com/ http://www.peercreations.com/ http://www.openbm.de/ http://www.powermarks.com/ http://www.riffs.com/ http://client.pluck.com/pwe http://www.searchfox.com/ http://www.shoppersbase.com/ http://shakk.us/ http://www.searchles.com/ http://www.saveyourlinks.com/ https://sourceforge.net/ http://www.sitejot.com/ http://smarking.com/ http://sitebar.org/ http://www.startaid.com/ http://sportslister.com/ http://socialbookmarking.org/ http://www.sync2it.com/ http://www.smelis.com/ http://www.urlblaze.com/ http://unalog.com/ http://www.urlex.info/ http://www.taggly.com/ http://syncone.net/ http://www.whitelinks.com/ http://www.wists.com/ http://www.wink.com/ http://www.whatlink.com/ http://www.web-feeds.com/ http://www.womcat.org/ http://www.carnatic.com/www http://www.wobblog.com/ http://www.wurldbook.com/ http://www.yourmarks.com/ http://www.zurpy.com/ http://www.zoogim.com/ http://www.lilisto.com/ http://www.spotplex.com/ http://www.spotback.com/ http://www.corank.com/ http://www.openserving.com/ http://www.openserving.com/ http://www.30daytags.com/ http://www.plime.com/ http://www.icerocket.com/ http://www.sphere.com/ http://www.netvouz.com/ http://www.mog.com/ http://www.vimeo.com/ http://www.ilike.com/ http://www.newsweight.com/ http://www.crowdfound.com/ http://www.spotonce.com/
Hi, here is the 20 dofollow SMO Site http://www.caroline-middlebrook.com/blog/do-follow-social-bookmarking-sites/ Thanks!
hi friend you must be visit at this thread : http://forums.digitalpoint.com/showthread.php?t=1047660&highlight=300+social+bookmarking+list
Hi Just i am also searching for the social bookmarking sites, thanks for your suggestions ,it would be a great deal to have the huge list of SBM sites
from this website you will get top 30 social bookmarking websites. ebizmba.com/articles/social30 Thanks, Brooke Thom