You will find here some scripts I've created for my own needs. Feel free to use them if you need :)
My scripts have been successfully tested on FF / Mac OS.
dotjs is a Google Chrome extension created by defunkt that executes JavaScript files in ~/.js based on their filename.
If you navigate to http://www.google.com/, dotjs will execute ~/.js/google.com.js and ~/.js/default.js is loaded on every request.
You can find more informations on defunkt's dotjs repository.