One of the best tools I have found thus far for backing up your settings and profile in Firefox is MozBackup. I have tried them all, and this freeware program is the one I keep coming back to.
MozBackup is a simple utility for creating backups of Mozilla Firefox, Mozilla Thunderbird, SeaMonkey, Mozilla Suite [...]

For those folks out there that are looking for another way to flip between browsers, I introduce you to Optool. I found this tool via Chris, and I do have to say for coming in such a small package (112 KB to be exact) it packs a lot of punch. You can switch [...]