So Mozilla labs announced their winners:
http://blog.mozilla.com/extendfirefox/2008/08/21/extend-firefox-3-winners
And I think that the 2 top winners are great.
Pencil will be a great tool to help people get ideas to paper (well documents).
And Read It Later is going to be a HUGE time saver for me as I normally open tons of tabs or bookmark stuff and never read it.