This morning I happened on a treasure trove of Firefox extensions; some of them allow you to easily back up your bookmarks, one of them remembers the tabs you have open(so if you crash or have to restart or something happens to Firefox, you can reopen Firefox and go back to the tabs you had open), and there are lots more!
There’s lots of goodies here, check em out:
[ http://www.pikey.me.uk/mozilla/ ]
And also, if you want an extension that allows you to back up your bookmarks remotely, try this one:
[ http://dietrich.ganx4.com/foxylicious/ ]
Give em a go, and leave a comment if you feel that any of them are particularly useful!