There are many sites on the Internet that carry sample stereo images - these are listed below. There is a lot of activity regarding stereo imaginmg with computers and the Internet, which is almost certain to lead to a boom in the number of people that are "stereo-aware" and "stereo-active".
Computer screen-based display devices cannot provide image resolution or image size anywhere near that provided by 35mm stereo photography with slide film. However the Internet certainly provides some excellent examples of stereo imaging - just remember that with the increased resolution of film, the "wow" factor increases too.
Local stereo photography clubs may be the best way to see stereo before trying out film-based stereo. If you do that, then make sure to get a look in a "stereo viewer" - which will provide results much better than any projection system.
3D Showcase by Boris Starosta
Studio 3D by Ron Labbe.
3D by Dan Shelley.