Yeah, I don't have a ton of add-ons either. But the ones I do have, I adore: Fox Clocks, Adblock Plus, All-in-One Sidebar, and StumbleUpon.
All-in-One Sidebar is like how I organize all my bookmarks, etc. All my stuff is in folders, etc. Love, love it!
And StumbleUpon, gah....so damn addicting. But I love it. You should definitely try it out. It basically takes you to random-ish (based on ur prefrences) websites. So you can discover lots of cool things.
You can take a look at my stumble upon 'profile' if you want to get an idea of what I mean:
holly984's favorite websites - StumbleUpon
I took a screenshot too, so you could see my firefox browser.
http://i194.photobucket.com/albums/z...Picture1-1.png
It is really simple, and those personas and stuff don't work on mine...so gray it is. You can also see the all in one sidebar thingy
Get it!! lol