List them:
- AdBlock Plus
- Flashblock
- NoScript (Best add-on ever next to Loop)
- Loop (take documents from your hard drive, combine them and convert them to PDF within Firefox
- DownloadHelper (allows you to download youtube videos, but you need a player that allows for the .flv extension)
- ForecastFox
- Google Preview
- Gmail notifier (icon on your status bar tells you if you have any mail without having to go to your physical gmail inbox)
- Download status bar (Eliminates the annoying Download Status box and reverts to sitting on your status bar when you download something