PCL is a Point Cloud Library that can be used with ROS or used separately to manipulate 3D data. It provides library functions to efficiently filter, segment, and register 3D point cloud data.
Check out the tutorials for more ideas as to what PCL can do. PCL should help keep you from reinventing the wheel when working with data from 3D sensors like the Kinect.
The special "Happy Birthday Bastian!" Edition 0.6 of PCL is now available. The new version 0.6 brings preliminary windows support in addition to already existing MocOS and Linux support. The full set of changes can be found here.