Invision - Prototyping and collaboration for design teams
Pexel - Pexel: Social Media Kit is a simple drag-and-drop Canva style Kit for creating quick social media creatives
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Dashboard UI Kit - A modern & responsive dashboard UI kit for designers.
Craftwork - A collection of User Interface resources made by Craftwork
Epic Pxls - UI kits, icons, templates, mockups and more, free