Anyone know any social networks that have groups such as yahoo groups, msn groups, google groups, facebook books, etc...
You should try Mixx.com - the whole point of the site is this : people creating groups around their and other people's interests. Also the site is packet up with traffic Other options depending on your niche would be Blogcatelog.com, BUMPZee or Myspace and the likes of it.
Hi You can try a new one, called club Together, its for UK and focuses on groups and clubs Its here Club Together Social Network
I'd stay away from Yahoo Groups. They're way overcrowded with spammers and it's extremely difficult to get people to post anything ligit and on topic. Even if something is started, it usually doesn't last long enough to have any effect. I don't know what to think of Myspace groups... They're basically just message boards with photo galleries... Although some people found favor in them, I myself found little use for them. I have no experience with MSN, Google or FaceBook groups.