Hyperwords
Just the Firefox extension I was looking for: Hyperwords. Mark text in your Firefox, hit Enter and…search the marked text on Google. Or Amazon. Or blog it. Or translate it. Dozens of choices. Or double-enter for Google search. Lovely 
/edit: This )/§% thing phones home! It has a button to deactivate “sending usage statistics”, but I don’t trust that it works. Such a lovely expansion, but I will not let it send “usage statistics” home. Too bad:(
/edit2: Well, after the comment (see below), I have decided to try it out again. Will report on it some other time!
October 26th, 2006 @ 17:12
Hi.
You can trust Hyperwords to not send stats if you turn it off. BTW, all it sends is what commands you use, not what you use it on. This is crucial for us to decide hwo to develop Hyperwords in the future. Hope you understand.
Frode
October 26th, 2006 @ 18:10
Well, that is actually nice to hear. I think I’ll just try it out again!