One of the most used features on my Powerbook is the two fingered scroll. The two fingered scroll is where instead of placing one finger on the track pad and using the mouse, you place two fingers on the track pad simultaneously and drag them. This allows you to move through a horizontal or vertical scroll bar with ease.
You can see an animation of this below:

This is a simple tip, but it’s a huge time saver. After using this feature day in and day out, I wonder how I ever lived without it.
Note: I believe this functionality only exists in G4 Powerbooks
Update: White Roses points out in the comments that the G4 iBooks also have this functionality. He also points out that if you’re stuck with an older iBook or PowerBook, you can still emulate two finger scrolling by downloading iScroll2.

White Roses
White Roses
Brian Mathias
http://www-users.kawo2.rwth-aachen.de/~razzfazz/iscroll2/ August 11th, 2005 at 7:03 pm
jonathan
jonathan
BoBB
Bill
Brooke
I too have the 1.33 model of powerbook that came out just before the scrolling trackpad feature was added. I use sidetrack instead of iscroll, but the principle is the same. You'd think Apple would just update the drivers of the older models to allow this. Obviously it's not limited by the hardware, because the third-party drivers make it work. August 12th, 2005 at 6:11 pm
Mike C.
Brad
I believe that's if there's a vertical and horizontal scrollbar. It will move vertical and horizontal at the same time. August 13th, 2005 at 5:17 pm
Mike C.
Jeremy Kemp
You can enable a circular scroll option, so that the trackpad acts like the iPod's scrolling touch wheel. With this enabled, you scroll down by circling clockwise and up by going counter-clockwise. August 17th, 2005 at 6:05 pm
Trackback
[...] this in the same folder as two fingered scrolling. To use this function, place 2 fingers on the track pad and click whatever you wish to right click. [...]
February 10th, 2008 at 1:17 am