Yes, indeed. At almost 65 years of age I have become a flex maniac.
The thing is, I recently read Richard Feynman's book Surely You're Joking, Mr Feynman. I was so fascinated with Feynman that I searched out a biography of the man and found one written by James Gleick, Genius: The Life and Science of Richard Feynman.
In this biography, brief mention is made of the discovery of the flexagon by Arthur Stone, a British colleague of Feynman's at Princeton University. Other students at the university became so fascinated with this apparently simple construction, made out of nothing more than a folded strip of paper, that they set up a committee to study the flexagon in its various configurations. One of the members was, needless to say, Richard Feynman.
Research into this interesting but apparently frivolous topic came to a halt with the war effort (Feynman went on to work on the development of the first atomic bomb, for example) and little more was heard of flexagons until Martin Gardner published an article about them in a 1956 edition of Scientific American.
Well, I've always liked paper-folding and have a sort of unfulfilled interest in maths (largely destroyed through conventional teaching methods), so flexagons sounded like something I needed to know more about. And, thanks to the Internet, that's a goal that is easy enough to achieve nowadays.
You might well enjoy making and playing with flexagons yourself, so here are some of the best sites that I have found. They range from simple starter sites to rather more complex ones that go into the theory behind these fascinating objects.
Jill Britton's Let's Make a Flexagon site is a good place to start if you've never made a flexagon before and want an easy introduction to see what it's all about. She shows you how to make a trihexaflexagon (one with six sides and three faces), including a video on how to fold it (folding is called flexing in flexagon-speak), and a full-sized template to print out. (The image accompanying this entry shows one of the faces of this flexagon.)
Aunt Annie's Crafts offers a good page for beginners, too. The first page presents numerous patterns and templates for trihexaflexagons and a sort of hidden link takes you to a second page with patterns and templates for hexahexaflexagons. (And there's another links for tritetraflexagons, those with three faces and four sides).
Keith Enevoldsen's Think Zone includes a page about flexagons that presents a very good looking example of a hexahexaflexagon (six sides and six faces) that Keith designed himself. Full instructions and templates are provided in a linked PDF. Excellent stuff.
Scott Sherman's Flexagon site is about as comprehensive as you'll find, with models ranging from the very simple to the very complex. Video instructions and demonstrations accompany plenty of templates that can be printed out for cutting and folding. Superb.
Flexagon.net also offers a wide selection of fascination flexagons. The site is perhaps more technical than Scott's and not as pleasant to navigate, but you'll still find plenty of variation and lots of templates.
Gathering for Gardner offers plenty of everything to do with flexagons, including a full collection of Vi Hart videos about the creatures and several excellent templates.
I am sure that there are many, many more resources out there, but I think that's enough to be getting along with. So from now on you have no excuse for being bored or having nothing to do. Get folding and flexing!