If you have a lower-end Canon digital camera, it's possible that you may be hack your camera to enable a bunch of high-end digital camera features like live histograms, depth of field calculations, under and overexposure highlighting, and shooting your pictures in RAW format.

You can get all of these features by upgrading the firmware on your Canon camera to use the CHDK firmware which is a free open-source firmware package that works on cameras that make use of the DIGIC II chips. To see if your Canon (or other) camera can be upgraded, check out the list of supported cameras here: http://scratchpad.wikia.com/wiki/CHDK/FAQ#Q._What_camera_models_are_supported_by_the_CHDK_firmware.3F

For a step-by-step tutorial on how to upgrade the firmware on your Canon camera to get this increased functionality, check out: http://www.linux.com/feature/118946