I just found an interesting feature in Firefox 2. If you have an open tab, then close it, you can right-click the tabs and choose 'Undo Close Tab' and the banished tab will return.

Update:

Jim Priest, who turned me on to the Microsoft Update Reboot Fix points out that the following key combos work:
CTRL+T = new tab
CTRL+SHIFT+T = restore last closed tab

I've use CTRL+T countless times. It never dawned on me to try CTRL+SHIFT+T. Thanks again Jim!