Sidetrack / iScroll 2 alternative, uses open source code, free available through SourceForge.
Allows old Powerbooks/iBooks without the native trackpad scrolling ability to perform different actions:
- Two-finger scrolling
- linear scroll regions
- hot spots for alternate mouse clicks
- remap the physical mouse button to any type of mouse click
- and more!
Very small app, just 300 kb, foolproof uninstaller available.