This one (answers.com) is one; then, there are lots of wikis and discussion groups. For example, you can contribute to Wikipedia. You can also search for discussion groups in any area that interests you.
KandeCorn.Piczo.Com
bungie.net?
Coolmath.net
tracpeople.moonfruit.com tycanyon.moonfruit.com
gracieandranda.webs.com
There are many "Cool" virtual game sites.
http://www.teenchat.com/
didgi draw on crayola.com
Dragon world . Com
Daily booth
cool math.com farm five.com addicting games.com whack your ex.com
some good websites are addictinggames.com primarygames.com miniclip.com cartoonnetwork.com