MachCloud found at the Mach3 website is a program that will convert point clouds to STL files. It's not too terribly difficult to figure out, not much in the way of help files or anything, but it gets the job done, and it's free.
http://www.machsupport.com/downloads.php
Look under "Artsoft recommended programs for MachCloud".
I've also been playing with MeshLab (have to search on the internet for it as I don't have the web address). It's a little more powerful than MachCloud, still free, but have a problem with it crashing when trying to open an ascii point cloud file. I suspect that whatever format I'm trying to open is not what it's expecting.
He is more machine now than man.....