I used to use aebutton but it would crash on me on occasion and it took a while to load on startup.
I use the following keyboard configurator:
http://forum.ppcgeeks.com/showthread.php?t=71233
It replaces the TP hardware keys driver and allows you to remap any button (including keyboard keys, home, back, start and end keys). There's no program running in the background and it just works. Highly recommended.