I've been using a LowePro Fastpack 350 for the last 3 years. It holds all my current equipment, a 5d Mk II, 24-70, 70-200 IS, a 50mm, 2 flashguns and a whole load of accessories, batteries and memory cards. It is a tight fit right now. Although there is a second compartment which has space for extra gear if you don't mind it rattling around or misc stuff. And has a nice slot for my 15" laptop to go in.
I'm thinking of getting a 7D as a back-up body soon and some more lenses so I'm thinking about getting a Think Tank Airport Accelerator or Addict soon. It has more space for but is slightly more compact and great for travel which I do a lot of. Now if I can just get my head round spending +/- $300 on a backpack instead of a lens.