Involve - Get behind-the-scenes access to your favorite nonprofits
Affimity - A social network with interest-specific channels, like on TV
All or Nothing - Competitive donations for causes you care about.
Topick - Gather around your favorite topics.
The Groundwork Donations - Seamlessly collect donations on your website
Slashdot - News for nerds, stuff that matters. Slashdot (aka /.