The Interaction Design Foundation is making free and open educational materials for all of interested audience all across the globe. This is what their mission is: “There are so many great minds in the Human-Computer Interaction and Interaction Design community and we want to empower these authors to reach all their interested readers around the world. We believe these authors have the minds to change the world and deserve a publishing venue truly designed for the author and the reader, not the publisher and the profit.” Some of the authors include the likes of Clayton Christensen, professor at Harvard and a NY Times bestseller, Steve Mann, the father of wearable computing and one of the founders of MIT's Wearable Computers group in the Media Lab, Tom Erickson, a veteran researcher at IBM's Research Center and more great names. Interaction Design Foundation offers a one year membership for $200(a limited time offer, membership only for $144), just a simple sign up and you are good to go.
source : Interaction Design