Lily is a Firefox add-on that allows users to create rich, complex applications in a web browser. With Lily it's possible to make programs that mashup the web or the desktop, visualize and animate data, modify webpages, play music, or connect to world outside the computer.
TiddlySnip is a Firefox extension that lets you use your TiddlyWiki as a scrapbook! Simply select text, right click and choose 'TiddlySnip selection'. Next time you open your TiddlyWiki file, your snippets will be there, already tagged and organised.
FireStatus is a Firefox 3 extension that allows you to send status updates, notes and URL links simultaneously to multiple social networks and services, like Twitter, FaceBook and FriendFeed. It also displays updates from these services in notification popups, for a more "live" communication with your friends.
CoLT (short for "Copy Link Text") is a tiny extension for Firefox which makes it easier than ever to copy a hyperlink’s associated text. For example, if I were to use this extension to
PicLens transforms your browser into a full-screen, 3D experience for viewing photos and videos across the web. With one click, PicLens makes online media come to life via an immersive presentation that goes beyond the confines of the traditional browser.