Top 6 Social Networking Sites as of Nov.

just a quick list:

1. MySpace - 58.8 million unique visitors.
2. Facebook - 19.5 million unique visitors
3. Classmates Online - 13.2 million unique visitors
4. Windows Live Spaces - 10.3 million unique visitors
5. AOL Hometown -7.9 million unique visitors
6. Linkedin - 4.9 million unique visitors

list of social networking sites

Check here for all the latest, I will repost as I find them:

Name	Description/Focus
43 Things	Tagging
Advogato	Free Software and Open Source developers
aSmallWorld	European jet set and social elite
BlackPlanet.com	African-Americans
Bebo	Schools and colleges
Blue Dot	Link sharing
Broadcaster.com	Video sharing and webcam chat
Blurty	Blogs, based on LiveJournal
Bolt	General (music and video)
CarDomain	Car enthusiasts
Care2	Green living and activism
Classmates.com	School, college, work and the military
Consumating	"Consumeetings"
Couchsurfing	"Couchsurfing"
Cyworld	Young South Koreans
Dandelife	Collective narratives or "shared biographies"
DeadJournal	"Dark" blogs, based on LiveJournal
Dodgeball.com	Mobile location-based service, owned by Google
DontStayIn	Clubbing (primarily UK)
Doostang	Careers
Ecademy	Business
eSPIN	Teen Dating
Facebook	College/High School students
Faceparty	British teens and 20-somethings
Flirtomatic	Flirting/Dating
Flickr	Photo sharing
Fotki	Photo sharing
Friends Reunited	School, college, work, sport and streets
Friendster	General
Frühstückstreff	General
FUPEI	General (Photo, Video, Music, Games, Event, and Chat Room)
Gaia Online	Anime and Games
Gazzag	General
Geni.com	Families, genealogy
GoPets	Virtual pets
Graduates.com	School, college, and work
GreatestJournal	Blogs, based on LiveJournal
Grono.net	Poland
Hi5	General
Hyves	General; focus on students and Dutch speakers
imeem	Instant messaging
IMVU	3D chat software
IRC-Galleria	Finland
iWiW	Hungary
Joga Bonito	Football (soccer)
JuiceCaster	General
Last.fm	Music
LinkedIn	Business
LiveJournal	Blogging
LunarStorm	Sweden
MEETin	General
Meetup.com	General
MiGente.com	Latinos
Mixi	Japan
MOG	Music
Multiply	"Real world" relationships
MySpace	General
myYearbook	General
Netlog	European young adults (14-24). Formerly known as Facebox.
Nexopia	Canada
orkut	Owned by Google
Passado	General
Phrasebase	Foreign Languages (education)
Piczo	Teenagers, Canadians, photo sharing
Playahead	Swedish teenagers
ProfileHeaven	British teens
RateItAll	Consumer ratings + social networking
Reunion.com	Locating friends and family, keeping in touch
Rimzu	Sociometric rankings
Ringo.com	General
Ryze	Business
Sconex	American high schools
Sportsvite	Recreational Sports
Studivz	University students, mostly in the German-speaking countries
Stumbleupon	Websurfing
TagWorld	General (tagging)
TakingITGlobal	Social action
The Student Center	Teens and colleges
Threadless	Custom T-shirts
Travellerspoint	Travel
Tribe.net	General
Twitter	Update friends with your status through SMS, IM, web interfaces
Vampire Freaks	Gothic industrial culture
Vox	Blogging
WAYN	Travel & Lifestyle
WebBiographies	Genealogy & Biography
Windows Live Spaces	Blogging (formerly MSN Spaces)
Xanga	Blogs and "metro" areas
XING	Business
Xuqa	Colleges
Yahoo! 360°	Linked to Yahoo! IDs
Yelp	United States adults
Zaadz	Social consciousness

Social Networking 3.0

If there were a competition for "Internet Buzzword of the Year," last year's winner would have been "social networking," as a cohort of companies such as Ryze, Tribe, LinkedIn, Friendster, Spoke, and Visible Path, rolled out new or improved services that let Web users create online mirrors of their circle of real-life acquaintances. The idea was mainly to let users build online profiles that advertised their interests and to help them connect with friends and friends-of-friends around one of those interests -- whether it be finding a job, making a sale, or repairing an old motorcycle.

But with the exception of Friendster and Myspace, the initial response to these services among average Internet users was sluggish. Many users signed up for one or more services, created online profiles, formed connections with a few acquaintances, and drifted away, uncertain about how to use the networks.

But today, not only have all of these companies survived; they're experiencing record growth, introducing new technology and new money-making features, and being joined by sophisticated new competitors such as iMeem. Moreover, they're joining the parade of sites offering "rich media" -- the big buzzword of 2005 -- by encouraging users to share their own content online, including photos, videos, music, and other digital files.

Social networking, in other words, is finally becoming a real business with a convincing product.

"A year ago a lot of our users were pretty unclear about what they could do," says Konstantin Guericke, co-founder and vice president of marketing at LinkedIn, a social network focusing on business connections. "They knew they were getting invitations to join the network, and they knew how to accept invitations, and sometimes they sent their own invitations -- but they weren't sure what else to do with that."

A year later, LinkedIn's membership has grown from 1 million to 4.2 million; users are conducting 5 million searches a month for potential contacts within their own networks, and the company has launched several revenue-producing features, such as paid subscription options that allow members to search profiles outside their immediate circle of friends and friends-of-friends.

Rather than simply passing requests for introductions back and forth through their networks -- which was about all they could do a year ago -- LinkedIn members are using their networks for practical purposes, like finding job candidates, locating business and legal services, and coordinating group activities.

What makes all this possible, says Guericke, is the user-generated content LinkedIn holds in its members' profiles, such as resumes and testimonials. "First, we are a search engine. But second, we are a publishing platform -- about yourself and what other people say about you," Guericke says. "It just creates a more powerful business."

http://www.technologyreview.com/Infotech/15908/