Facebook Design - Devices - Images and Sketch files of popular devices.
Device Shots - Generate high-resolution device mockups using a screenshot.
Design Cell - Beautiful multipurpose mockups for iOS
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Clay Mockups - Free set of beautiful device mockups for your designs
Screen Size Map - An interactive map of screen sizes for responsive web design