I've been working on a project to integrate Lua with the Firefox web browser, in the form of an extension which adds support for the language to write background services or on-demand applications to run directly in the browser.
I have yet to write more code to get the integration working. I will enter this project into the Mozilla Lab's extend Firefox Contest. So hopefully, I'll have enough implemented by the deadline.
For more information, please see the Google code project page.
Image courtesy of ladyphoenixx_1999 (CC-BY-NC-ND)