I've been using firefox for at least a year now, and have just begun messing with add-ons. I just downloaded the one that lets you download youtube clips and the like. Awesome!! (I know, I'm late to that bandwagon.)
I also downloaded mousegestures, which is cool, but I don't really use it much since its just ingrained in me these days to use the toolbar. I forget I have it.
What other add-ons does everybody use here or recommend?
I like the weather one. Gives you temperature down at the bottom of the browser. I also like the IE tab to test stuff out sometimes if you do that kind of stuff. You can see how things look in IE...
I use Adblock Plus (magically removes all ads from all web pages) cusomise google, fasterfox, forecastfox, foxytunes, gmail notifier, ie tab, mouse gestures (only for the mouse rocker gestures), stop-or-reload button and stumbleupon to name a few.