For use on the bike, in the kayak, and for dh to take on motorcycle runs, we have a Pentax Option 43WR. The WR stands for water-resistant. It's a small, square-shaped camera, not too terribly slim, but nicely grippable. 4 mp, 2.8 optical zoom. And I got a neoprene cover that zips onto it and gives it a little bump-protection.

The rating is called "water-resistant," but I've personally had this camera in my pocket, unintentionally rolled my kayak, and the camera was fine. It's not for diving--I think it's only good a couple of feet below the surface, but it can take a dunking like a champ.

Picture quality is not something you'd want to use for your kids' graduation, but it's great for what we use it for. Fits in a large pocket, a small handlebar bag, and I'm thinking it would also fit in a bento box.