gimp-ufraw (ubuntu hardy) would open cr2 files from my new camera (Canon Digital Rebel XSi, aka 450D), but until I applied a patch the colors were all wrong. (This is on launchpad but not fixed in an official ubuntu package yet)

Another nice tool with this camera is gphotofs, which allows the camera to be mounted as a filesystem even though it uses PTP rather than mass storage. The one packaged for Ubuntu Hardy works nicely.