uControl is a great little tool to remap the ‘unused’ keys on you Mac. It touts the ability to remap Caps Lock, other modifiers, and even convert the Function Key into a ‘scroll button’, so when you hold it down, you can track up and down with the trackpad.

Update: The official 1.4.6 release is out, with support for MacOS 10.3.8. Use that, instead. :)