MockMagic - A free, easy-to-use device mockup generator
Facebook Design - Devices - Images and Sketch files of popular devices.
Dimmy.Club - Device mockup generator for your website and app screenshots
Clay Mockups - Free set of beautiful device mockups for your designs
Mockup Generator by Pixeltrue - Create beautiful product mockups in just a few clicks
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.