A collection of free design resources from the designers at Facebook. Facebook Design Resources currently includes: the previously featured Origami, a prototyping toolkit for Quartz Composer; Diverse Device hands, a set marketing images of various smartphones held by two different diverse hands; a complete iOS 9 iPhone GUI for Sketch and Photoshop; and a Medium blog covering the designers experiences. It's already a great collection, but I'm sure they are planning to add more soon.