Most often, I use the Lowepro Nature Trekker with the following gear:

•  Nikon D2X bodies
•  Nikkor 500mm f4D AF-S or Nikkor ED 200-400mm f/4 lens
•  Nikkor 300mm f4 AF
•  Nikkor 80-200mm f2.8D AF
•  Nikkor 12-24mm f2.8D AF
•  Nikkor 105mm Micro-Nikkor f2.8D AF
•  Nikon SB24 with extension lead
•  Better Beamer
•  Lee polarising filter
•  45cm diameter Lastolite reflector clipped on with a carabiner
•  52cm diameter diffuser in outer pocket
•  Allen wrenches
•  Jeweller's screwdrivers
•  spare batteries
•  Lexar compact flash cards
•  portable hard disc

My carbon fibre Gitzo tripod is carried by hand.