Nathan @ Linux.com has a great how-to on making a cheap Cannon camera better with a firmware mod, he writes –

If you have a point-and-click digital camera made by Canon, you may be able to turn on all sorts of features usually reserved for more expensive SLRs. That includes live histograms, depth-of-field calculation, under and overexposure highlighting, and — best of all — shooting your pictures in RAW. The secret is CHDK, an enhanced, free software replacement firmware.

HOW TO – Give your low-end Canon digital camera RAW support – Link.