I'm moderately interested in stereo photography. I started by taking a few by using the cha-cha technique
with mixed results. I wanted a little better control without a lot of expense or bulk and my first gadget
was a slidebox. I put a
1/4"-20 TPI thread insert into a piece of 1/2" thick hobby wood scrap. Cut the length equal to your camera's
width + the distance between your eyes (average is
65MM or 2-9/16"). Glue and clamp some rails on 3 sides. You can use the slide box sitting on a flat surface
or mounted on a tripod or clamp-on unipod.

Not much to look at, but it works great.

Take a picture, slide the camera against the opposite rail and snap another, later combine them
with the GIMP ... there are even plugins to help do this easily if you wish to use them.