Warning! Some information on this page is older than 5 years now. I keep it for reference, but it probably doesn't reflect my current knowledge and beliefs.
Wed 27 Apr2011
I have Canon PowerShow A610 digital camera. Today I've found a unofficial, free, powerful firmware for it, as well as other models from Canon. It's called CHDK - Canon Hacker Development Kit. Installation is quite easy and totally safe - it's enought to put the software onto SD card. On Windows this can be done with CardTricks application. The firmware adds some useful features, like:
New HUD elements: battery indicator, free memory, live histogram
Bracketing - for exposure, aperture, ISO and focus
Saving RAW/DNG files
Zebra - highlighting of overexposed and underexposed areas
File browser, calendar, Basic/Lua scripting, some games and much more.
I recommend this firmware to anyone who owns a Canon camera. Mine now looks like this: