Top Social Networking services.

MerchantCircle.com
LinkedIn
Myspace.com  
Facebook
Reddit.com
twitter.com
Digg.com
YouTube
Buzznet.com
hi5.com
Windows Live Spaces

Classmates Online
AOL Hometown  
Reunion.com
AOL People Connection
Club Penguin

Top Social Networking Sites of General Interest

1.    MySpace: Started in 2003, MySpace still maintains the largest userbase.
2.    Facebook: Facebook was opened to the public in 2006.
3.    Hi5: A fast-growing social network with a strong base in Central America, has over fifty million users worldwide.
4.    Ning: A social network for creating social networks, Ning takes the idea of groups to a whole new level.

Top Niche Social Networking Sites

1.    Flixter: Flixter combines social networking with movie reviews.
2.    Last.fm: Social music site, allows members to create their own radio station that learns what the person likes and suggests new music based on those interests.
3.    LinkedIn: A business-oriented social network, members invite people to be "connections" instead of "friends." is a contact management system as well as a social network, and has a question-and-answer section similar to Yahoo! Answers.
4.    Xanga: A social blogging site that combines social networking elements with blogging. Members earn credits for participating in the site and can spend credits on various things such as buying mini-pictures to post in the comments of a friend's blog.

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