ive just got the new lowpro fastpack 300 and its pretty good. not the biggest but can get 30d with 24-70mmL, a 50mm, sigma 15-30mm, 70-200mmL and a 580ex flash. best is it will also take a 17" macbook pro. its also got a bit of storage in the top for bits and bobs. the other nice thing is you get your camera out of the side without having to open the whole bag up, like a lowpro slingshot.