Where can I get Rapid? I was watching this video by CorridorDigital and I heard them mention Rapid. I can't find it on Google. Could someone link me to it.
It appears to be RapidForm which has now been bought out (or changed name possibly) to 3D Systems Geomagic.  The website is here.  I found this by looking for mesh refinement software matching the term Rapid and that seemed likely the best match.  In particular, it appears to be GeoMagic XOS.  I don't personally have any experience with the particular software.

Basically the point behind the software is to make refined meshes from a point cloud.  3D scanners like the Kinect don't actually form a mathematical model, instead, they generated large numbers of points at a given distance from the sensor.  These points are formed into a cloud which then has to be modeled into a vector based solid mesh for rendering purposes.

This process is actually incredibly similar to converting a bitmap image into a vector graphic, but it has to be done to produce smooth, solid surfaces in 3d, so it's a bit of a complex and specialized operation.  Software like this allows for the best fit mesh to be found and to ensure that it makes a solid, detailed mesh that doesn't have holes in it that could cause problems with the geometry.