These are the FOURCCs I know about that refer to compressed formats (the ones that you see displayed when you don't have the right codec installed to play a given AVI file). If you know of any more, please drop me a line.
Quickjump:If you can't find the codec you are looking for here you may want to look at my help page where this is a list of the codecs I have heard of but have absolutely no information on.
If you are confused by any terms, you may find help on the video-related acronyms page.