The Greasemonkey extension has long been one of our favorite tools for Firefox, allowing us to bend the web to our will with light and simple scripts written in JavaScript. Now most Greasemonkey scripts work in Chrome, no extension required.
Firefox with Greasemonkey: If you find search results on popular search engines like Google, Bing, and Yahoo Search to be a bit bland, Colorful Search will color code and group your searches for easier identification.
Firefox: Gmail recently made a few tweaks to its message count API, leaving tools like the favicon message indicators by Eric Bogs and Peter Wooley, along with Gina's own Better Gmail 2 Firefox extension, broken. Now they're fixed.
The nightly builds of Google Chrome's open-source foundation, Chromium, includes a feature that might mean great things for Greasemonkey fans. Click on a user script file, such as at UserScripts.org, and Chromium asks to install it as a working extension.
Every time you click results in Google, Yahoo, or Bing, a special URL tracks your click—and makes it annoying to copy and paste. The CyberNet blog runs down click-track-preventing tools for all three search engines.
Firefox with Greasemonkey: If you're going to spend your time on Facebook, you can at least make it quicker to browse through and confirm that nothing earth-shattering has occurred. A simple Greasemonkey plug-in assigns Facebook sections to simple keyboard buttons.
Firefox with Greasemonkey: Previously mentioned Stylish script Google Reader Absolutely Compact removes a lot of the Google Reader interface to get more on-screen, but for some it takes away too much.