The latest PowerBooks to be released come preinstalled with drivers that enable trackpack scrolling. This means that instead of having to use your arrow keys to navigate through long documents or oversized web pages, you can scroll directly from your trackpad.
From the Apple website:
Scrolling through web pages or large documents on a trackpad can challenge even the most nimble fingers. That’s why every PowerBook G4 features a new trackpad with scrolling capability. Just drag two fingers over the trackpad to scroll vertically and horizontally or pan around any active window. Change this feature to suit your needs: Customize your trackpad settings or turn off scrolling completely via System Preferences.
This is such a great feature, and thanks to the publicly released driver and a guy called Daniel Becker, you can install this driver on your own iBook or PowerBook. All you have to do is run a little system check and download the driver you wish to use. I’m currently rocking the X/Y scrolling driver and it’s great. I recommend you install this driver!