Rated 5 out of 5 stars
This is a MUST HAVE plugin for every user (or developer) who wants to alter the currently viewed page to their liking, be it adding functionality or simply changing the look of it. It makes browsing your favorite sites much easier and more convenient since you can simply write your own user script to tweak them to your liking or download an existing one from one of the many user script hosting sites.
Greasemonkey really does alter the web quite literally! :)