Use CSS to place Firefox tabs where you want them
I actually hacked this up for myself a couple of months ago and the explanation of how I did it was sitting in the queue waiting to be posted here (like 30+ other things at the moment), but it seems that I’ve been preempted by mozillaZine, which I was just informed, has some instructions on the process.
I like everything on my computer to be on the right (tabs, system dock, application drawers, etc); for me, it makes perfect sense both from an efficiency standpoint (i.e., it’s usually the case that my mouse pointer sits on the right side of my screen) and a screen real-estate standpoint (i.e., my monitor, like most, is wider than it is tall).