MScheme - Lisp in Mozilla. › Steve Jenson's blog

Back in 2002, I wrapped a Javascript Scheme interpreter in XUL and put it up on the web. I've finally gotten around to making an installer for it

It's missing a lot of functionality, and even a menubar, but it works well enough for learning how XUL and XPI packages work.

Clicking on the 'Install MScheme' link will automatically install it under Mozilla. Unzipping it will show you how an XPI installer works.