A while back Aaron offhandedly shows me a slick trick with Firefox when I'm complaining about how it doesn't show namespaces on xml documents: you can use view-source as a protocol to look a website's source code. If you've got Firefox, check it out.
I've been making my way through the 5th edition of the Rhino book and Flanagan shows another technique of using your address bar with a protocol. You can type something like:
Of course do not forget about:config as a way to configure Firefox. Any more of these goodies?