5D with battery-grip and strap.
580 EX flash
24-105 f4 IS L -or-24-70 2.8 IS mounted (with lens hood)
70-200 2.8 IS L (fits upright with hood)
1.4x tele-extender (or 50mm 1.4 with hood)
16-35 2.8 L
Epson P-5000 (80GB Portable storage unit)
Lumiquest pocket bouncer kit with three different inserts
(gold/silver/white)
8 extra AA batteries
4 extra 5D batteries
Timer remote shutter release
Bubble level
Small (but sturdy) Bogen/Manfrotto table pod with ball head
CF card case (holds 4 cards)
Blower brush
My trusty cheapie shower cap (for body in rain)
Flashlight
Other misc. odds and ends.

Other configurations go into it when my intentions dictate (macro, low
light, etc.).