This project is archived and no longer mainted.
Check out its successor, which is way better and runs on all platforms:
dotjs  is a  Google Chrome  extension  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.
This makes it super easy to spruce up your favorite pages using JavaScript.
On subdomains such as http://gist.github.com dotjs
will try to load ~/.js/gist.github.com.js  as well
as ~/.js/github.com.js and ~/.js/com.js.
Bonus:  files  in ~/.js  have jQuery 1.9  loaded,
regardless  of  whether  the  site  you're  hacking
uses jQuery.
Double bonus: ~/.js/default.js  is loaded on every
request,  meaning you  can stick  plugins  or helper
functions in it.
GreaseMonkey user scripts are great, but you need to
publish them  somewhere and re-publish  after making
modifications. With dotjs, just add or edit files in
~/.js.
$ cat ~/.js/github.com.js
// swap github logo with trollface
$('a[class^=header-logo-]').html(
    $('<img>')
        .attr('src', '//bit.ly/ghD24e')
        .css({'width': 'auto', 'height': '22px'})
    );
Chrome extensions can't access the local filesystem, so dotjs runs a tiny web server on port 3131 that serves files out of ~/.js.
You don't have to worry about starting or stopping this web server because we put a pretty great plist into ~/Library/LaunchAgents that handles all that for us.
The dotjs Chrome extension then makes ajax requests to http://localhost:3131/convore.com.js any time you hit a page on convore.com, for example, and executes the returned JavaScript.
- OS X
 - Ruby 1.8
 - rake (gem install rake)
 - Google Chrome
 /usr/local/binin your $PATH
git clone http://github.com/defunkt/dotjs
cd dotjs
rake install
Now open https://localhost:3131 in Chrome and follow these steps:
- Click the "X" Padlock icon in the address bar
 - Click "Certificate Information"
 - Drag the large cert icon to your desktop
 - Open it with Keychain
 - Configure its Trust section as shown: http://cl.ly/Pdny
 
Finally install the Google Chrome extension:
rake uninstall
- Icon: http://raphaeljs.com/icons/
 - jQuery: http://jquery.com/
 - Ryan Tomayko for:
 
"I almost wish you could just stick JavaScript in ~/.js. Do you know what I'm saying?"