I'm always a little depressed when someone beats me to writing a cool article, and this one was on my list. In this case, however, Adam Pash at Lifehacker has done a fine job of explaining a neat hack for many consumer-grade Canon point-and-shoot digital cameras. CHDK, for Canon Hacker's Development Kit, is a non-destructive firmware enhancement that adds six categories of features:

1. Enhanced ways of recording, including support for raw format images, longer video times, and additional video compression options.
2. Additional data on the camera's LCD, including a histogram, battery life indicator, depth of focus, and more.
3. More photographic settings, such as longer exposure times, faster shutter speeds, and automatic bracketing of exposure.
4. Scripts that can automate various camera functions. Scripts are written in a version of BASIC. With these scripts, you can do things like take multiple photos with different exposures, or even take a picture when the camera detects motion.
5. Remote control of the camera (either taking a picture or running a script) via the camera's USB connection.
6. Various new capabilities for the camera, such as a file browser for the memory card, games like Reversi, and so on.

CHDK works with a number of Canon models, though not all of them, so you'll need to check the compatibility list before going any further (and no, as far I can tell, no other manufacturer's cameras have any CHDK-like hacks). What's especially nice about CHDK, apart from all the useful functionality it provides, is that it modifies the camera's firmware only when you explicitly load it, and everything is back to normal when you next power up the camera. Have fun hacking!