Poly by Google is a library of free 3D objects for augmented and virtual reality apps.
threed.io is a browser based tool to generate custom device mockups on the fly. Upload your Designs, make adjustments and download your custom mockup! Even works pretty nice on mobile. We're still in beta, but if you're interested in threed, please read the about text on the site.
MR Builder is a new way for architects, 3D designers and constructors to visualize 3D models.
MR Builder allows to demonstrate and interact with your 3D models in Hololens. Just a couple of clicks in almost any 3D editor, like 3dsMax, Revit, SketchUp and others and you ready to go