Source: http://lifehacker.com/5635936/build-a-one+camera-3d-photography-rig
We've mentioned ways to build a 3D photography rig with two cameras, but DIYer countervideo realized that with just a few mirrors, you can do it with one.
You may lose a bit of resolution in your photos over the two-camera method, but if you don't feel like spending the money on two whole cameras, this is by far a better way to go. All you need is a camera and some mirrors—no post processing necessary.
The whole thing is just made from two large mirrors and two small mirrors, as well as some acrylic to hold the mirrors up and a large plate to put it all on. Apart from the mirrors though, the rest can be of any material you want, so you won't have to search too hard for the parts to put it together. Hit the link for more information.