One addition to the list would be the Sustainable Futures Foundation - social network for social investing. On this issue I encourage everyone to check out xigi.net.
Go2web20.net is the best resource I've found for tracking new tools and companies offering social media services. It can - of course - be searched by tag. Currently, there are no tags for philanthropy, nonprofits, donors, giving, etc. and sites like GiveWell or Smartocracy are not on there. (Go ahead, folks, suggest them - it is community media after all). As for blogs on web2.0 stuff, my regular reads are read/write web and the aggregator Web2.0 Workgroup. For blogs that look specifically at where web 2.0 meets nonprofit work, check out Beth's Blog, Marnie Webb's ext 337, Britt Bravo who blogs here, here and here ,and netsquared. And don't forget Allison Fine's old medium (its a book!), Momentum which you can find out about on her blog.