Here is one that does work in FF4 Rated 1 out of 5 stars

OK, the old version on this page don't work any more on FF4. But don't be sad.
Here is a link to a new version which I installed on FireFox 4.0 final release and it seems to be working perfectly. I love it. I've been saved!
https://addons.mozilla.org/en-US/firefox/addon/tab-history-redux/