I discovered a few plugins for Firefox, two of which are from Mozilla Labs. A disclaimer: These are all non-final versions, and therefore might be buggy. However, I have not had any real difficulty with any of them.
Ubiquity allows you to use the keyboard to quickly Google something, select text and email it to someone, or insert a map into an email and email it to someone, and more. But hitting -, you call Ubiquity, which then will do your bidding.
Second, a program called Auto Dial, which, based on your web history, builds a custom web page that opens each time you open a new tab, so that when you open a new tab, it will
Finally, a program called Ctrl-Tab allows you to switch between tabs easily, all the while seeing what tab you will be switching too.