With Scroll Reverser, you can invert up and down scrolling on OSX, so it acts like iOS. This feature is rumored to be coming to OSX Lion, so here's your chance to try it out.
The app is simple to install, and uninstalls fully when dragged to the trash. When active it's unintrusive, and the scrolling reverse is effective. Now, when you drag down, pages will scroll up, just as in iOS.
You can choose to have Scroll Reverser open at Startup, and also hide the status bar icon if you wish. The experience of Scroll Reverser will be odd to begin with, but you will soon get used to it.
Scroll Reverser lets you scroll up and down in the same way as touchscreen iOS devices.