Paul Battley told me about this nice extension for Mac OS X:
iScroll2 is a modified trackpad driver that adds two-finger scrolling capabilities to supported pre-2005 PowerBooks and iBooks on OS X 10.3 (“supported” meaning those which have a “W-Enhanced” trackpad, including most AlBooks and recent iBooks).
To enable scrolling mode, just place two fingers on your trackpad instead of one. Both fingers need to be placed next to each other horizontally (not vertically). Some people get better results with their finger spaced a little bit apart, while others prefer having the fingers right next to each other.
Very cool, though I still prefer a real wheel-mouse.
NP: Dan Bern—In God’s Time