Needing an update. My apologies.
A record of resources mentioned in my blog.
Martin Gardner Essay
The article was first published as “Hexaflexagons” in The College Mathematics Journal Vol. 43, No. 1. pp 2-5. It’s available on JSTOR. Here’s a link to a preview: http://www.jstor.org/discover/10.4169/college.math.j.43.1.002?uid=2&uid=4&sid=21104040486031
Printable Hexaflexagon templates
Foldable templates and ideas: http://www.pinterest.com/kmp444/foldables/
Paper with STEM education: http://technolojie.com/454/