Generally, to play mods you just have to unzip them in the same directory as your Madness Interactive download and run the .exe/.swf/.html/whatever's in there. Even if you're using a Mac and can't run the MI download, this technique will still allow you to play most mods. If the mod comes as a .swf and you are having trouble running it, try opening it in your web browser.

      If you're interested in making a mod, have a look at the source code page. You'll need, at the very least, Macromedia Flash MX. If you're new to Flash you should probably practice with some other stuff before you try modifying Madness. If you're comfortable with Flash but having trouble with the source, see this Madness modding tutorial by Teh Marz. It's very good, provides both walkthroughs and sorely needed documentation. You shouldn't contact me about for modding help, because I don't really remember much about the code and won't be able to help.