pretty much the same as everyone else:

-adblock (must have)
-adblock filterset.g updater (must have)
-forcastfox
-pdf download (fairly usless i think)
-tabbbrowser preferences (must have)
-ieview (must have)
-foxytunes
-colorful tabs
-stumbleupon (good for wasting time)
-fireftp (useful for my modding work)
-searchpluginhacks (must have, keep it around in case someone sneeks an engine into my search bar)