If you happen to have a S5 (or s3 among other Canon models) there is a utility firmware that you can run inside your camera and many new cool features to your camera such as storing RAW images!  One of the parts I am the most excited about, being a software developer for almost two decades, is the ability to write scripts that run inside my camera and automate some functionality.  Here is a starter:

http://chdk.wikia.com/wiki/S5IS

After a bit of browsing though, it appears if you are using a memory card greater than 2GB, you will need to go through some extra steps.  Here is an excellent step-by-step post on how to handle large cards:

http://mind-fields-ahead.blogspot.com/2008/04/canon-s5-is-chdk-hack-step-by-step.html

I have yet to try this as I do not have a card reader that works with my large card, but I am ordering one :)

BTW, it seems I am not the only one excited by the ability to take decent pictures (his better exposed than mine though ;)):

http://mind-fields-ahead.blogspot.com/2008/05/to-moon-and-back.html