Mainstream & Large Scale Social Networks
Name:URL:
Netloghttp://netlog.com/
Platinum Loungehttp://www.platinumlounge.com/

Twitterhttp://twitter.com/

Embeddable Widgets
Name:URL:
Clearspringhttp://www.clearspring.com/
Qoofhttp://www.qoof.com/
Sprouthttp://sproutbuilder.com/

Blog Plugins
Name:URL:
AddThishttp://addthis.com/
ShareThishttp://sharethis.com/
Zemantahttp://www.zemanta.com/

Social News
Name:URL:
Help a Reporter Outhttp://www.helpareporter.com/
Hubdubhttp://www.hubdub.com/
regatorhttp://regator.com/

Social Networking Applications
Name:URL:
Artitionhttp://www.artition.com/
Digsbyhttp://www.digsby.com
Ping.fmhttp://ping.fm/

Social Bookmarking
Name:URL:
AddThishttp://addthis.com/
Diigohttp://www.diigo.com/
ShareThishttp://sharethis.com/

Search & Social Search
Name:URL:
Artiklzhttp://www.artiklz.com/
findingDulcineahttp://www.findingdulcinea.com/
Scourhttp://www.scour.com/

Sports & Fitness
Name:URL:
FitFiendhttp://www.fitfiend.com/
Gymineehttp://www.gyminee.com/
OneSeasonhttp://www.oneseason.com/

Photo Sharing
Name:URL:
flickrhttp://www.flickr.com/
ipernityhttp://www.ipernity.com/
TinyPichttp://tinypic.com/

Video Sharing
Name:URL:
ffwdhttp://www.ffwd.com/
Vimeohttp://www.vimeo.com/
YouTubehttp://www.youtube.com/

Start Pages
Name:URL:
Googlehttp://www.google.com/
iGooglehttp://www.google.com/ig
Yahoo!http://yahoo.com/

Places & Events
Name:URL:
City Datahttp://www.city-data.com/
Doodlehttp://www.doodle.com/
Muchmorhttp://www.muchmormagazine.com/

Travel
Name:URL:
CouchSurfinghttp://www.couchsurfing.com/
GeckoGohttp://www.geckogo.com/
Spotted by Localshttp://www.spottedbylocals.com/

Music
Name:URL:
Last.fmhttp://www.last.fm/
NoiseTradehttps://www.noisetrade.com/
Pandorahttp://www.pandora.com/

Social Shopping
Name:URL:
A Full Cuphttp://www.afullcup.com/
Pikabahttp://www.pikaba.com/
Tigerbowhttp://www.tigerbow.com/

Fashion
Name:URL:
Chictinihttp://www.chictini.com/
Coolspottershttp://coolspotters.com/
Polyvorehttp://www.polyvore.com

Celebrity & Gossip
Name:URL:
Bollyscoopshttp://bollyscoops.com/
Oh No They Didn’thttp://community.livejournal.com/ohnotheydidnt/
Superficial Galleryhttp://www.superficialgallery.com/

Mobile Applications
Name:URL:
Evernotehttp://evernote.com/
MocoSpacehttp://www.mocospace.com/
Viigohttp://viigo.com/

Dating & Romance
Name:URL:
DateHookuphttp://www.datehookup.com/
SpeedDatehttp://www.speeddate.com/
zooskhttp://www.zoosk.com/

Wiki
Encyclopedia Dramaticahttp://encyclopediadramatica.com
wikiHowhttp://www.wikihow.com/
Wikipediahttp://www.wikipedia.org/

Politics
Name:URL:
CreateDebatehttp://www.createdebate.com/
Politics4allhttp://www.politics4all.com/
PreciseNewshttp://www.precisenews.us/

How-to
Name:URL:
A Full Cuphttp://www.afullcup.com/
College-Cramhttp://www.college-cram.com/
Howcasthttp://www.howcast.com/

Environmental
Name:URL:
ecomiihttp://www.ecomii.com/
gazellehttp://www.gazelle.com/
neighBorrowhttp://neighborrow.com/

Non-Profit Causes
DiscoverScholarshttp://discoverscholars.org/
SocialVibehttp://www.socialvibe.com/
Stop Political Callshttp://stoppoliticalcalls.org/

Online Games
Name:URL:
Armor Gameshttp://armorgames.com/
Playfishhttp://www.playfish.com/
Powerpetshttp://powerpets.com/

Niche Social Networks
Name:URL:
Lymabeanhttp://www.lymabean.com/
The Star Trackerhttp://www.thestartracker.com/
Wadjahttp://us.wadja.com/