If, like me, you have 3-4 browser tabs you like to have open all the time (Gmail, Greader etc), then the Permatab and Faviconize add-ons are for you… unless you use Firefox 3.6, out a couple of days ago, which breaks the former.
A little Googling this morning found me App Tabs, a great alternative. Recommend it.
Whilst I was searching, I also found this info on how to turn on the CTRL-TAB tab preview feature in FF 3.6 – which is pretty awesome.