One thing I found missing from the new release of Firefox is a button for the toolbar that allows you to easily send the current webpage as a link. I got used to this functionality when I was still using Flock.
I found an extension that adds a Send Link button and it works just great. Maybe the final release of Firefox 3 will have the send link button included, but I don't expect it to be because release candidates normally have all functionality that a final release will have.
Get it at the Mozilla add-ons web site.