Install Firefox Add-On [firefox 1.5 - 3.0b]
Note: This wasn't working properly before, but I have fixed the MIME type for .xpi with my server and all is good now.
Install Greasemonkey User Script
Note: Ooops, I left a bug in the GM script. I will fix it soon *promise*
If you are looking for a version compatible with IE 6, IE 7, Opera and Safari head over to the bookmarklet version.