A bit of meta-coverage: A Fist Full of Euros notes that “A recurring theme in all the commentary of the attacks is the stoicism, composure and defiance of Londoners.” [1]
Heiko Hebig points out that the bombings occurred even though London has one of the most comprehensive networks of security cameras in the world [2].
Lenin's Tomb has a long post analyzing the various interpretations and possible consequences [3] of the bombing.
Barcapundit points to [4] an article that details the similarities–and the differences–between the London bombings and the bomb attacks in Madrid a few years ago.