There are plenty of online services to make a lenticular print of your 3-D photos, and it's easy enough to make your own stereoscope-compatible prints. And, of course, 3-D monitors are inexpensive these days and provide an easy, high-quality way to view your photos. And if not that, there's always anaglyphs.
But I wanted to make View-Master reels, and I spent some time searching for a service to print them for me. (There are services that will print the slides, and sell you the cardboard and glue to assemble the reels yourself--a fine option, but a lot of by-hand work. Here in the 21st century, surely someone can print the whole reel at once!)
I did finally find a service which I'm pretty happy with. The reels aren't cheap, at $20 for a single reel with 7 photos (but most of this price is for set-up; you can print multiple copies at sharply reduced prices), and the resulting images are really grainy--much detail is lost at this scale. This is not the way to appreciate the fine quality of a well-crafted stereo photo. But even with all that, there's nothing quite like the way people react when they look through a View-Master and see their own face within, in 3-D. Everyone knows what a View-Master is and how to use one, and everyone has a soft spot in their deep, childish heart for them.
I have no affiliation with this web service, but I do recommend image3d.com for anyone who's willing to accept these caveats for a piece of red plastic joy in their hands. Although their primary business seems directed at people who think it's a good idea to make non-stereo View-Master reels from ordinary 2-D photos (which seems pointless to me), they also do offer a well-hidden service where you can upload 7 MPO's, cropped to 1112x955 pixels, and they'll print them into a stereo reel for you. You can find the link for this service here: http://image3d.com/stereo/ .
David