There have been a couple of requests here and on the pyglet mailing list for my code to perform pixel-perfect sprite collisions. I finally had a bit of down time, post-exams, and put together a demo, complete with source code.
The source is pretty clear, and thoroughly commented, so it should be very easy to follow. The demo is very simple, but the concept translates to more complex applications as well.
Let me know if you have any issues, or questions about the source, and note that it does require a fairly recent version of python (2.5+, for generator expressions and the built-in set class).