This extension allows you to explore Wikipedia by adding a related articles side pane to Wikipedia. Additionally, it allows searching of highlighted text on Wikipedia from the right-click context menu.
The Whys between follows on the Web. Browser plugin to assist in finding out why people follow the people they do on Twitter.
|Twitter Search Box|
Using Greasemonkey, this utility enables you to enhance twitter.com by adding a search box to search tweets and help you find out what's happening right now.