I used the Lowepro Off Trail 1 for about 10 years with my old Canon SLR. It is a minimalist waistpack, just big enough for your camera and attached lens. It comes with two detachable lens compartments which give you the flexibility to either leave them at home or bring them along. I used it for rock climbing/mountaineering and liked it because it was small, sits close to your body, and is easily accessible.
The problem is, it is a bit small for my K10D, so I am thinking about moving up to the Off Trail 2 which is a bit bigger. Also, my DA14 doesn't fit very well in the lens compartment.
I think they also make one called the Photo Runner which is specifically designed for runners and cyclists, but I have no experience with it.
I also have a Zing, which is an ultra-minimalist neoprene case that tightly wraps around your camera. It seems to provide decent protection and isn't much bigger than the camera. The problem is it has no strap, so you have to use your camera strap. Plus, when you take it off, it either just hangs from the camera which is annoying, or you have to shove it in your pocket or something. It is good if you are shoving the camera in your pack and want some (minimal) protection or don't mind throwing the camera over your shoulder like a messenger bag.