free social bookmarking site according Page Rank

PR9 sites
http://www.netscape.com/

PR8 sites
http://del.icio.us/ - PR8
http://www.furl.net/ - PR8
http://www.digg.com/ - PR8
http://www.technorati.com/ - PR8
http://www.stumbleupon.com/ - PR8
http://www.rojo.com/ - PR8

PR7 sites
http://myweb2.search.yahoo.com/ - PR7
http://www.fark.com/ - PR7
http://reddit.com/ - PR7
http://www.43things.com - PR7
http://www.mister-wong.de/ - PR7
http://de.lirio.us/ - PR7
http://www.newsvine.com/ - PR7
http://ma.gnolia.com/ - PR7
http://www.simpy.com/ - PR7
http://www.citeulike.org/ - PR7
http://www.nowpublic.com/ - PR7
http://www.rollyo.com/ - PR7
http://www.jeteye.com/ - PR7
http://www.blogpulse.com/ - PR7
http://www.icerocket.com/ - PR7
http://kinja.com/ - PR7
http://www.kuro5hin.org/ - PR7
http://www.tailrank.com/ - PR7
http://meneame.net/ - PR7
http://www.clipfire.com/ - PR7

PR6 sites
http://www.shadows.com/ - PR6
http://www.backflip.com/ - PR6
http://www.blinklist.com/ - PR6
http://www.blinkbits.com/ - PR6
http://www.blogmarks.net/ - PR6
http://www.diigo.com/ - PR6
http://bluedot.us/ - PR6
http://www.feedmarker.com/ - PR6
http://linkfilter.net/ - PR6
http://www.netvouz.com/ - PR6
http://www.spurl.net/ - PR6
http://adoppt.com/ - PR6
http://www.gather.com/ - PR6
http://www.trailfire.com/ - PR6
http://www.backflip.com/ - PR6
http://www.bloghop.com/ - PR6
http://www.wurldbook.com/info/ - PR6
http://www.clipclip.org/ - PR6
http://www.clipmarks.com/ - PR6
http://www.rawsugar.com/ - PR6
http://www.linkarena.com/ - PR6
http://www.listible.com/ - PR6
http://popurls.com/ - PR6
http://thumblicio.us/ - PR6
http://dev.upian.com/hotlinks/(source list is currently frozen for a while) - PR6

PR5 sites
http://www.shoutwire.com - PR5
http://www.corank.com/ - PR5
http://www.ambedo.com/ - PR5
http://www.blogmemes.net/ - PR5
http://www.feedalley.com/ - PR5
http://www.gravee.com/ - PR5
http://www.jeteye.com/ - PR5
http://www.lifelogger.com/ - PR5
http://www.linkagogo.com/ - PR5
http://www.millionsofgames.com/ - PR5
http://www.myhq.com/ - PR5
http://www.mylinkvault.com/ - PR5
http://www.myvmarks.com/ - PR5
http://www.openbm.de/ - PR5
http://tags.library.upenn.edu/ - PR7
http://www.peoplefeeds.com/ - PR5
http://www.phigita.net/ - PR5
http://www.pligg.com/ - PR6
http://segnalo.alice.it/ - PR6
http://www.shoutwire.com - PR5
http://www.squidoo.com/ - PR6
http://www.stylehive.com/ - PR5
http://unalog.com/ - PR5
http://buddymarks.com/ - PR5
http://www.hanzoweb.com/ - PR5
http://www.linkroll.com/ - PR5
http://supr.c.ilio.us/ - PR5
http://www.butterflyproject.nl/ - PR5
http://www.Givealink.org - PR5
http://www.favoor.com/ - PR5
http://www.lilisto.com/ - PR5
http://linkatopia.com/ - PR5
http://www.markaboo.com - PR5
http://uvouch.com/ - PR5
http://www.tagtooga.com/db.tag - PR5

Hot for 2007:
http://www.rockyou.com/
http://www.stickam.com/
http://www.zingfu.com/
http://www.mybloglog.com/
http://www.trailfire.com/

Other:

http://www.myspace.com/
http://www.facebook.com/
www.bebo.com
www.blackplanet.com
www.xanga.com
www.imeem.com
360.yahoo.com
www.classmates.com
www.hi5.com
www.tagged.com
www.livejournal.com
www.gaiaonline.com
www.friendster.com
www.orkut.com
spaces.live.com
www.hoverspot.com
www.buzznet.com
www.sconex.com
www.migente.com
www.myyearbook.com
http://slide.com
http://zwinky.com
RYZE.com
LinkedIn.com
ZeroDegrees.com
MeetUp.com
Tickle.com
Spoke.com
Hipster.com
Tribe.com
DudeCheckThisOut.com
http://www.piczo.com/
http://twitter.com/
http://www.care2.com/
http://ryze.com/
http://www.blackplanet.com/
FriendSurfer.com
PeepsNation.com
http://www.asmallworld.net/login.php
http://www.broadcaster.com/
http://www.buzznet.com/
http://www.consumating.com/
http://www.couchsurfing.com/
http://dandelife.com/

10 most beautiful social networks:

http://virb.com/
http://trig.com/
http://www.purevolume.com/
http://9rules.com/my/
http://www.pownce.com/
http://flickr.com/
http://threadless.com/
http://www.shelfari.com/
http://www.beautifulsociety.com/
http://www.humblevoice.com/