Tutorials using the Render > 3D Transform filter to create a 3D box from 2D images.

* http://www.spoono.com/photoshop/tutorials/tutorial.php?id=26
* http://www.heathrowe.com/tuts/3dtransform.asp
* (.pdf) http://itc.umcrookston.edu/Tutorials/Adobe%20Photoshop/Document/3D%20Transformation%20Tutorial.pdf
* http://biorust.com/index.php?page=tutorial_detail&tutid=4

Also see this thread (http://www.retouchpro.com/forums/showthread.php?t=11799) for Photoshop actions and a link to a free plugin.