I came accross this nice Linux development project called 'CHDK'.
It is a bunch of software that you can load onto most (not all) canon powershot compact digital
cameras in order to release their hidden potential!
It can make your camerea do long exposures (up to 65 secs) or very fast exposures (1/25,000 sec),
you can record images in RAW format and display a live histogram. You can even run scripts to take bracketing pictures or on motion detection.
At linux.com you can find a nice overview by Nathan Willis.
Unfortunately, my camera is not supported (yet). But if anyone fancies trying it on your (older) powershot let me know how it works out.