Is it a Synaptics pad? If so, the driver that comes with Ubuntu should have every option you need for sensitivity, tapping and scrolling. There are many wiki articles around to tell you how to configure it.
If you want the fancy multitouch gestures, you can check out this project, it isn't very advanced yet, but has some of the features that are in OSX.
http://bitmath.org/code/multitouch/