Facebook Design
Facebook Design offers some of the best, high quality device mockups, UI kits, images and more. To be used by designers and developers for free.
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Apple Marketing Resources
Apple’s Developer Marketing Resources offer great mockups for all their devices, free to use when designers and developers want to market their work.
Mockups Design
Mockup`s Design is a simple site where designers can find premium-quality free mockups, to use in their projects.
Mockup Hunt
Mockup Hunt is a huge collection of the best free mockups hand-curated from the most trusted mockup websites. Their collection is updated weekly.
Mr.Mockup
Mr. Mockup offers free high quality Photoshop (PSD) mockups to showcase your design work like a pro!