I use a lowepro passport sling, it's great because I can carry my D300 with a grip in the expandable section, then when i put the bag on and get the camera out I can zip up the collapsable part of the bag and it's nice a compact. But It can still carry my 80-200m, flash and a spare slide in battery pack for the grip, as well as a bottle of juice, poop bags for the muttley, as well as other bits and bobs, and it only cost me about £20 ish.