Social Media websites to check out (feel free to add more):
http://www.metafilter.com
http://www.reddit.com
http://www.delicious.com
http://www.digg.com
http://www.flickr.com
http://www.mashable.com
http://www.metacafe.com
http://www.secondlife.com
http://www.stumbleupon.com
http://www.technorati.com
http://www.twitter.com
http://www.youtube.com
http://www.facebook.com
http://www.brizzly.com
http://www.m-trends.org/
http://www.mrc.org/public/default.aspx