The idea behind stereophotography is getting actual depth out of a photo. You have two eyes. The slight difference in viewing angle between your two eyes allows you to judge distance, or perceive depth. So if you take two images from a slightly different perspective, you should be able to view them with depth.
To view stereophotographs, cross your eyes. The two side-by-side images should become three images. The one in the middle is the one you want to carefully focus on. It's similar to viewing Magic Eye pages. If you do it right, the middle image will seemingly be in 3D. It makes you feel like you're AT the location, rather than looking at a photograph of the location. Here's one I tried to take of my living room last night.
click to enlarge, or see it on Flickr
This one was less of an actual photograph (really crappy composition, etc.) and more of an experiment to see if I could get the effect to work. It works. There's not a whole lot of depth in the shot to see, but the technique was successful. I'll definitely have more interesting stereo shots in the future. But here's one of my favorite stereophotographs of all time.