Mod your iBook's Apple logo
This isn't really a new mod, as I've seen it bounced around the internet in the past (over a year ago). Nevertheless, it is a cool little mod, so when I saw it on MacSlash today, I thought I'd join in the net-reminder. MacMine has a tutorial up on how to change the color of the Apple logo on the back of your iBook's screen. It's a pretty low-risk mod, although removing the backing of the iBook will void your warranty.
You can colorize your PowerBook's Apple logo, too.