I like my Pentax Optio S4. It fits *inside* an Altoids can, which is a convenient protective case. The only drawback of this 4MP camera, in my opinion, is the difficulty it has with action shots. It was given top nods by the folks at Bicycling magazine for size and shot quality, for what its worth.
A new release from Pentax (honest, I'm not a spokesman for them) is water resistant, which would be really nice. Check it out at:
http://www.pentaxusa.com/products/cameras/camera_overview.cfm?productid=18197
Greg