I try to carry a Kodak Easy share (350 I think). It is good for me as that is the same one they issued at work. I can carry a spare simm card and always get 'that shot'.

I don't EDC a camera, but my wife's a photog and we generally have at least one around. If you want something small and simple, you might try a 110 mini camera like this. No batteries required. I have one. Haven't done much with it, but short of spy gear, it's about the simplest, least complicated setup you'll find. Film's cheap, though not available everywhere anymore.

The tinycams yahoogroup people seem to like the Aiptek PenCam SD seen at http://www.2fidelity.com