I’d like to bring the attention of everyone who hasn’t yet seen this to the following website.
iScroll 2.

Basically this driver allows you to enable two-finger scrolling, like on the new powerbooks, on your slightly older one.  I’ve been using it on my 15”, 1.25GHz powerbook, and it’s brilliant.

Two-Finger scrolling is a pretty cool idea, and while it’s rather awkward at first, it’s possible to get the hang of it, and make use of it when working with your touchpad, if you don’t want to reach over and press a key, or click a scroll bar.