Ask any developer, having a utility library available when building applications can save a you a lot of troubles. As part of a project to create gestural based character movements in second life (Armadillo); John McCaffery has developed NuiLib, a library which works with the Kinect in order to alleviate much of the heavy lifting and provide a means to ease integration of NUI devices into applications.
Another innovative and praticle use of the Kinect depth sensing capabilities is proudly on display for this latest hack which involves using the device as a parking aid. Once only available as a premium feature in some vehicles, this clever application uses the Kinect along with a few open source solutions such as OpenCV, Ubuntu and Libfreenect to pull it all off.
Written as a project for a PhD research project, TouchTable allows Windows users to use any flat surface as their own mouse free, multi-touch interface with the use of a Kinect sensor.
With this software you'll be able to use your finger to control the mouse cursor, left mouse click by touching the surface with your index finger, right mouse click by sticking your thumb out while taping with your index finger and drag and drop by holding your index finger down and dragging it across the surface.