I use a PC keyboard to go with my MacBook at home, which is fine until I need to use a keyboard shortcut that starts with Command. Then I sometimes get pretty confused figuring out just where the Command key is.
In Leopard, I can set different Modifier Keys for different keyboards, so I remap ALT to Command and WIN to Option on my PC keyboard. Here's how:
Mac OS X Hints
http://hints.macworld.com/article.php?story=2007102013195255