Seeing as I plan to format and re-install my computer any day now (I've been putting it off due to time constraints for a month now) I was wondering the best way to back up Firefox, especially with all the cool extensions I have.

LifeHacker gave me the answer with the Firefox Extension Backup Extension

FEBE and CLEO together do the job of my recent Firefox extension packs feature – but the whole process seems a bit easier. The extensions are still a little buggy (I had trouble getting CLEO to work), but this is a nice step forward in making extension packages that are easy to move around and install. You can package up all of your extensions, save them some place handy (I'd probably keep one in my Gmail), and install the .xpi any time you've got a fresh profile or install of Firefox. Windows only, for now. — Adam Pash