I am not using Firefox to much recently as Chrome has become my default browser, but I do still like to use some extensions which keeps Firefox installed on most of my computers. I don't use too many, and they typically are installed to help me either collect or consume information better. I put together my current set of extensions using the new Firefox Collections tool. Noting terribly shocking in the collection, but I think this is a good set if you want to keep your extensions to a minimum. I supplement these extensions with a few bookmarklets.
Image via CrunchBase
Bit.ly Sidebar - Which makes it easy to send links to Twitter, Facebook or via Gmail.
Note in Reader - This is mostly replaced by Feedly, but sometimes I use it when I am having issues with the Feedly minibar.
Amazon Wish List - I use Amazon to track the things I want to buy for myself and others.
Facebook - Sometimes I post directly to Facebook.
Posterous - I am playing with Posterous to make posting to my blogs and various services easier.