Here is a guide to install Natural Scrolling for Linux on Ubuntu 11.10. You can use Natural Scrolling to reverse the direction of scrolling. With Natural Scrolling, you push or scroll your fingers or mousewheel upwards to move the page content downwards (and downwards for upwards) just like on iOS devices. You can install Natural Scrolling using the zedtux PPA for Apple Natural Scrolling.
To add the PPA and install natural scrolling open a terminal window (press Ctrl+Alt+T) and copy+paste the following lines:
sudo add-apt-repository ppa:zedtux/naturalscrolling
sudo apt-get update
sudo apt-get install naturalscrolling
When installed close the terminal window and to start natural scrolling press the SuperKey and type: natural scrolling. When started an indicator will appear in the top panel, right click on it to enable/disable natural scrolling. To start natural scrolling at login right click on the indicator and select Preferences and enable Start at login.