Hi I have just purchased a Lowepro aw trekker plus .
I manage to fit a canon 350 D body with a 100- 400 mmlenses attatched into the bag Plus a 17-40 L ,17-55,55-200,50 mm into the bag plus spare battery numerous filters,cards 580 flash unit a 15.4" screen laptop and still have room to spare.This back also a place to store your tripod.
The pack itself is well padded shoulder straps,a tummy strap and chest strap its makes for comfortable wearing fully loaded
heres the link:
http://www.lowepro.com/Products/Back...r_Plus_AW.aspx