Partnerup: Use your skills to help other startup businesses! In tough times this site could help some of us find other new opportunitities, and others who are looking for help, find new help.
Seeking Alpha: A very active community of those interested in investments. Mostly useful stuff, but be careful though as some posters are quite crazy!
Venture Beat: The place to go for those interested in venture investments
Newser: For those of us who are more visually oriented, important news sorted out visually..