I came across this easy to set up mouse control Kinect hack for Ubuntu. From what I can tell, you can't execute any "click" commands so it isn't the most practical hack out there. It may however prove to be a good jumping off point if you were interested in developing a Minority Report type interface for Ubuntu.
If you've been following the Kinect hacking and development scene for as long as I have, there's a good chance you'll rememeber the Keyboard Anywhere hack. It was one of the first real eye openning Kinect hacks to hit the scene and for good reason. It combined the futuristic interface of an invisible keyboard that could be placed anywhere (hence the name) with a great memory from back in the day.
libfreenect is the end result of the famous Adafruit Kinect hacking bounty X-Prize winner. After it made its mark on the scene, the OpenKinect community was born and the rest is history. This guide will provide the resources necessary to install the OpenKinect libfreenect drivers for Ubuntu. The original installation guide can be found at OpenKinect's Getting Started Guide.