I posted a nice link on digg (you know you want to digg it... dooo ittt) for a demo of Fitt's Law (fine here is a direct link).

It has some really good experiments that go along with the background information (read: clicking games). Some of it is common sense, but a good refresher nonetheless. Fitt's law of design basically explains some of the commonality of good button placement and why user can more effectively navigate certain things (from a psychological perspective). yeah.