If you use Firefox on multiple machines, they have finally released Weave 1.0 which allows you to sync settings and bookmarks across multiple machines for free.
You can go to the add-ons page and search Weave. You’ll be asked to make an account after installing the add-on and then you can tell it what information you want to sync (or how to merge it if you’re setting up the second one).
They give you the option of saving the information on your own host server if you have one or you can use theirs, which is a nice feature of this.
*Note, I do believe you must be running Fx 3.6 (as you should be anyways)*