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.”
Heiko Hebig points out that the bombings occurred even though London has one of the most comprehensive networks of security cameras in the world.
Lenin's Tomb has a long post analyzing the various interpretations and possible consequences of the bombing.
Barcapundit points to an article that details the similarities–and the differences–between the London bombings and the bomb attacks in Madrid a few years ago.