Engineer Andy Barry has created a new budget open source 3D scanner. He calls it the MakerScanner and hopes to sell it through the MakerBot web site for around $200. It uses the same laser line, offset webcam than many other systems use. He does a good job of explaining on the MakerScanner.com web site. There are even more details on his web site and Thingiverse.
The system uses galvanometers to move a mirror which moves the laser line. A sine wave is output to one galvanometer so it creates a line from the laser diode. The other scans it across the model. All of the parts appear to be printed with a Makerbot.