Greasemonkey is a Mozilla Firefox extension that allows users to install scripts that make persistant changes to specific web pages. You can alter the layout of a page, disable the advertising, add links to other services.
The screenshot shows Gmail Saved Searches script in action.
Use Greasemonkey (required: install Firefox)
1. Download Greasemonkey
2. Find scripts
3. Learn more about Greasemonkey (free ebook with videos)
4. Greasemonkey hacks (get the code)
5. Greasemonkey hacks (buy the book)
16 minutes ago