Which Firefox Extensions Do You Use?

One of the primary reasons I love Firefox so much is the all the extensions that are available. Here’s a list of all the extensions I have installed, and that I use on a regular basis:

  • Feed Your Reader: Lets external
    applications and web based aggregators use RSS autodscovery (extremely useful).
  • HTML Validator: Adds HTML validation to the View Page Source of the browser.
  • MeasureIt: Draw out a ruler to get the pixel width and height of any elements
    on a webpage.
  • Scribe: Ads Word Processor like functionality to web forms, including opening
    and saving for entries as files. (Good for weblog posting.)
  • Aardvark: Allows cleaning up a page prior to printing it. Also has page analysis
    tools for web developers (which is mainly what I use it for — I hate printers).
  • Web Developer: Adds a menu and a toolbar with various web developer tools.
  • Live HTTP Headers: View HTTP headers of a page and while browsing.
  • SpellBound: Adds spell checker support to web forms and extensions.

What extensions am I missing that you can’t live without?