http://www.marcmoini.com/sx_en.html
its called Smart Scroll...it's awesome, it lets you use the "momentum" of your scroll to keep scrolling when you stop touching your tracpad (also works with mice, but it might seem weird)...It's awesome, i suggest you try it. you can also reverse your scrolling so that when you move from left to right the document moves from left to right just like on an iphone or ipod touch. its very cool try it