Whether for real business or just light games, there are social networks aplenty.
Here is a small list of the ones I am currently aware of. If you know of any others, let me know. Oh yes, some of these are more social/interactive then others.
Please check them out and post your review in the comments section.

http://12seconds.tv/

http://blip.fm/

http://www.vimeo.com/

http://www.slacker.com/

http://twitpic.com/

http://twitter.com/

http://www.myspace.com/

http://www.facebook.com/

http://www.youtube.com/

http://www.justin.tv/

http://www.blogtv.com/

http://www.stickam.com/

http://www.ustream.tv/

http://www.migente.com/

http://www.linkedin.com/

http://www.slide.com/

http://jpgmag.com/

http://www.playlist.com/

http://www.blackbook2.com/

http://www.kyte.com/

http://qik.com/

http://www.flickr.com/

http://www.stumbleupon.com/

http://www.thebridgemaker.com/

http://www.blogger.com/

http://www.last.fm/

http://songza.com/

http://www.tokbox.com/

http://www.skype.com/

http://www.oovoo.com/

http://www.omgpop.com/

http://dailybooth.com/

and finally

http://ning.com where you can create your own social network