There used to be an old myth that said stereo manufacturers basically sold the same stereo and added and removed holes in the casing depending on the price. You paid $100? You got a volume slider. Paid $1,000? They cut the holes for a whole EQ set.
CHDK is kind of like that, but it isn’t. Designed to work with Canon consumer point and shoots, CHDK is a homebrew firmware that adds RAW, timelapse, and histograms to cameras that wouldn’t normally have these features out of the box. By using the sensor’s full capabilities — unhobbled by the commercial firmware — you basically get a more powerful camera for the same amount of money. Lifehacker has a full tutorial on installing the firmware and you can get more info at the CHDK wiki. Happy snapping, but just don’t try to cut holes in your camera to find those hidden settings.