For those of us who are keyboard fiends, <a title="adot's notblog* "firefox, cats, mars, and more"" href="http://weblogs.mozillazine.org/asa/">asa reports on DougT's new Firefox builds with spacial navigation enabled.
Essentially this lets you navigate through all the links on a page using the up, down, left and right arrows. This saves you tabbing through stuff.
You can grab a test build here. I hope that this will get into the default FF build - it is low impact and doesn't need a UI, but it's another one of those features that could keep it a little bit ahead of the game.