The American Journal of Play is a publication dedicated to promoting play of all types. A combination of science, research, interviews, and book reviews, it is published four times a year and shares the latest information about why play matters. We all know that, but its nice to know there is work completely based around it.
“Sometimes I Pounce on Twigs Because I’m a Meat Eater” looks especially good to me - the importance of active, outdoor play.
And if you're in Rochester, New York...the Strong National Museum of Play.