The most thorough coverage I've seen of the London attacks is in Wikipedia, of all places. The site also has an excellent image gallery, including a screenshot of the communique claiming responsibility for the murders.
I could say more, but I'm trying to respect Kevin Drum's call for "the blogosphere on both left and right to refrain from political point scoring over the London attacks. Just for a day." Tomorrow I'll find a way to pin the blame on Kelo, the FCC, and the obnoxious blogger of my choice. Today I'll just mourn.