Wired is running a good piece on what exactly the RAW file format is, and why you should always use it on your digital camera. It is a good reminder that most compression formats cheat us out of precious (but now cheap and plentiful) data bits, either through “lossy” algorithms or their very proprietary nature.

update:  It was pointed out that in fact many RAW formats themselves are proprietary.  This is a good point and care should be taken to be sure you store your images in an open format like PNG for the long haul.