I have a rather small bag, but i find it workes great for me!
I can fit all my camera stuff into it. and i have 2 memory cards, the big ipod goes anywhere in it the SB600, the Nikond40x with the 18-55mm the battery charger along with my minatrue tripod and the spare battery!
its something along these lines: http://products.lowepro.com/product/Nov ... 72,20.htm#
and i think the bag wasnt really expensive, but i cannot recall the price at the moment, iw ill have to find the receat for that, and i m very happy with it as i like to travel light
i have used this in the swedish winter....and had no problems so far, and i have used it in the austrian alps at the end of january month....