Linux.com provides a detailed explanation of how to get the most out of your Canon camera:

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.

Even more interesting than the advanced picture control features is access to the scripting/automation language:

When you get comfortable with CHDK, you can check out user-supplied scripts. CHDK’s scripting environment uses a simple BASIC-like language that lets you write your own scripts to automate camera functions — but not to create whole new features for the camera. User-contributed scripts are available on the CHDK wiki, and implement interesting functions like HDR stacking, focus bracketing, time-lapse movies, and lightning photography.

Whoa, Bessie. How do you trust those scripts? Could there be malicous or mischevious consequences? Despite those risks, I’m now more tempted to buy a Canon (I have traditionally used everything but Canon, with a focus — ha ha — on Nikon and Olympus) than ever before.