When I was in JCPenney a couple of months ago I picked up a pair of Dockers Carry-On bags for about 30 bucks each; they're made of ballistic nylon and have shoulder straps. Add some Domke inserts and they'll carry just about anything. No, really.
Otherwise I have my Mamiya 645 Pro in a Billingham 225, with a couple lenses and an insert or two. If I plan to be shooting a lot, I have a Billingham Hadley Pro loaded with several backs, more inserts, and plenty of film. There may also be another lens in there.
Right now in Spain they're holding the Running of the Bulls,
followed by the Soiling of the Pants, and the Burying of the Idiots.
I've been using a Lowepro Rover AWII to haul my RB67 around. It's a nice camera backpack with a padded bottom for camera stuff and a top half for trail mix or a flashlight. The bottom section holds the camera perfectly with the 90mm attached; however, the camera takes up the entire bottom half. Making holding other stuff, like lenses kinda difficult but you could always stash them in the top half. It has a lot of pockets to stash film, trail mix, or a light meter. It also has a handy waistbelt, chest strap deal and a tripod holder thingy which accommodates my Bogen 3011. Overall I like it, hauling the tripod, camera, and trail mix gets a little heavy but I'm young, 22, and I can handle the weight.
I almost went with a F64 bag but simply couldn't tell about the quality and construction with what photos were available online. I went into my local shop to test out virtually every single bag and ended up getting the Domke F2. It's quite perfect for me, really. Enough room for the 645AF, space for 3(2 MF, 1 35mm) lenses, some film, an extra film back and my F100 in one of the side pocekts, which are rather generous with space. Thanks to you all for your replies, really appreciated. I can't believe it took that long to find the right bag!
I use a beat to $#!+ army gas mask bag with two homemade dividers. It holds either a Rollei TLR or a Plaubel Makita 67 depending on which I want to shoot. One camera, one lens and not a lot of crap to haul around and confuse the issue. I can work fast and light.
And no one will think there is a valuable camera inside.