Firefox only (Windows/Mac/Linux): The Tabhunter Firefox extension adds quick keyboard-based tab switching to Firefox—sort of like Launchy for Firefox tabs. Just invoke Tabhunter, start typing, and Tabhunter searches for a match through all your tabs.

Everybody knows what Google is, and I can bet every Firefox’s user has used it once. If you are an obsessive Google’s user and want to add new features to it, today is your luck day. GooglePreview is a Firefox extension that inserts preview images into your Google or Yahoo search results, as well as sites’ popularity rank bar.

If you visit many webpages that require you to login everytime, if you are no speed-typist and your email is very long, or if you simply don’t want to type it anytime, this add-on is what you are looking for today. Paste Email is a Firefox add-on that memorizes up to 16 email addresses, and it lets you paste any of them into any login box with a single click.

We’ve pushed out Shareaholic v1.6! This release is a major update (hence the jump from v1.4.1 to v1.6), represents months of hard work, and should make a lot of you very happy as it incorporates lots of new features that you have been requesting!
* Shareaholic 1.6 adds support for 10 new services: Yahoo! Buzz
Improves support for:

I've been recently working with John Resig on his great Firebug extension called Fireunit. This very promising extension is intended as an automated testing framework for Firefox extensions and it should also be useful for testing web pages in the future. It's still at the beginning, but growing and starting to be very useful for testing Firebug itself.
Such unit test framework is what I have been waiting for a long time. Not only debugging and profiling is important and the unit testing was the missing piece in the Firebug world.