Craftwork - A collection of User Interface resources made by Craftwork
Supernova V4 - Turn Sketch into iOS, Android and React Native in minutes
Fabrx.co - Create the UI Kits, Bootstrap 5 or HTML Dashboards that you need in minutes. Have some design sense to spare? Fabrx will help you tackle even the trickiest of projects.
Free UI Resources - Download Latest Free UI Design Resources
Invision - Prototyping and collaboration for design teams
Angle 2 Mockups - A giant Sketch Library for creating app presentations