Without knowing what style of photography you intend to focus on, it's hard to recommend anything...
I've recently bought 2 "new" bags (for about $50 USD), but they are NOT specific camera bags. I use vintage military surplus canvas which, fortunately, is kind of trendy right now (and VERY cheap) where i live.
One bag is like a messenger bag, though kinda smallish,
http://www.sportsmansguide.com/net/cb/cb.aspx?a=445954
and the other bag is the SMALL (quite rare actually) Army ALICE rucksack made from 22oz milspec canvas.
http://www.harrys.com/index.php?main_page=product_info&cPath=33&products_id=598
I don't worry about the whole notion of having "waterproof" bags because a small garbage bag tucked in a pocket somewhere does the job just as well and is a whole lot cheaper.
Anyway, my selections are based on what/how i like to shoot - which is street photography. So for me, a bag that doesn't draw attention or look like it has something expensive in it works best for me. I usually have to add some padding, but "discreet" is what i need the most - especially when i am on a tram or trolley and "pick-pocket" thieves abound.
I've worked in law enforcement, the military, and other "intentional observation" vocations and learned that blending in with the local "styles" and not looking so much like a tourist is very helpful - especially for Americans.
HTH,
