Here are the things I've written that I'm not too ashamed to put online. Hopefully this list will grow.
If you do combinatorics with Maple, you'll want John Stembridge's packages, found here. You can see a few programs I wrote to go along with them here.
I've recently started writing Java applets. I've included the code in case it might help someone else learn the language, or in case anyone with more expertise and free time than I have wants to send me helpful critiques. Hopefully it won't be too long before I have some more complex and useful programs here.