AFAIK, most production surfboard companies are using this ( http://www.shape3d.com/
) or something like it. I know a couple kiteboard designers, and they're still designing my eye/hand, but I'd imagine alot of kiteboard design is done on some CAD app.
I've also tried using this ( http://www.freeship.org
) which is intended for boat/ship design, but I have been able to use it to start some basic shapes and then output the 3D file to another app.
For my designs in the past, I've done them entirely in 2D CAD (one template for the top view, one for the rocker line and another for a center profile). Not as sexy as doing it in 3D, but it works