The red/cyan anaglyphs have been around for decades now and they are still the most inexpensive ways to experience 3D. The idea is to capture a scene from two different points of view (by keeping the same kind of gap between the cameras as the human eyes) and then filter the left and right eye images through red and cyan filters. Finally the two scenes are superimposed on a screen or paper/film.
To be able to view these images, one needs glasses that can separate the two color components for each eyes as they were originally captured by that special camera arrangement. The glasses too, as you would have guessed, use the same color filters - red and cyan and the human mind is pleasantly befooled into perceiving depth in the scene (hence the sensation of 3D).
If you ever came across videos and pictures on the web that are anaglyphs and you did not have the means to view them right away, you may just follow the instructions here to make a pair of those glasses for yourself. Being lazy and shameless I made mine using transparent sheets of plastic and red/blue markers:
Once you are done, have a go at this flickr pool dedicated to anaglyph photographs. Youtube also has many 3D anaglyph videos. I watched whole of this video and believe me it was awesome.
As a closing note, don't let yourself believe that the approach described here is the only way you could view stereo-3D images. Vendors are already selling stereo-3D enabled products for some time now and if you need somewhat sophisticated (and less parsimonious) solution, you could definitely go buy them.