Recently installed this add-on and have been REALLY enjoying it and thought I'd mention it. I find myself having to copy and paste text often in Firefox, with this add-on simply highlighting any text will immediately copy it (no having to right-click or CTRL +C) and then to paste just click your middle wheel button.

https://addons.mozilla.org/en-US/firefox/addon/383



*EDIT: SpellingI love this add-on. I've been using it for a while.One user review at https://addons.mozilla.org/en-US/firefox/addon/383#reviews said it's not yet compatible with Firefox 3.6. Others also commented about some difficulty getting it to work with Firefox 3.6 but then others were able to get it to work with Firefox 3.6. Apparently, some USERS may need to change their approach to installation and setup before it works correctly with Firefox 3.6.

I'm still using Firefox 3..5.7. I think I will try this add-on. Still 3.5.7 here so couldn't say with certainty if it's 100% compatible.Mr. Tech Toolkit is your friend LOOOOL....I just realized, that my auto copy doesn't come from the above add-on, but from FasterFox, which has very same option.
Sorry for the confusion.