Most of these require expensive gear, and (or) are in one or other way limited. The way of looking at the result is also different, stereoscopes that show two separated pictures (one for each eye) and the ones with dots that you are supposed to change your eyes to see (gives me headache), or the holograms that requires a lot of expensive lasers and other gears.

      Then there is the most familiar one, with the two colored glasses, that often comes with magazines and such, it's called "anaglyph". The idea is that you have two different pics that are filtered with a red and a cyan filter, either when the picture(s) are shot, or in PS, then when they are matched together they will make a 3D picture, if observed through the colored glasses. The cons with this method is that you either need a stereo camera / special lens (expensive) or move your camera to take two shots. (limited to non moving objects, and a lot extra job in PS). An other downside is that these pictures are weird to look at without the  colored glasses.

      I happened to find an article on the internet about a lens that Tamron made 15 years ago, that had a built in filter that was half red and half cyan, it was supposed to give anaglyph 3D pictures direct on the film (sensor).

      I had an old lens , Spiratone 100mm 1:2.8, that I had bought at a flea market for $5, two pair of 3D glasses and an old broken lens with Nikon bayonet.

The first step was to make the filter, cut out a half circle from each side of one pair of glasses, made a circle frame out of thin cardboard to the size of the inner tube of the lens, and glued the flter halfs on the frame. Next step was to butcher the lens and get the filter as close to the aperture blades as possible, put the lens together again, like the second pic to the right shows. At last I figured out a way to attach the bayonet from the Nikon lens and magical I had a 3D lens.