Wannathis - 3d illustrations and freebies
Shapefest - A massive library of 3D shapes for everything!
Craftwork - A collection of User Interface resources made by Craftwork
Iconscout - Design Resource Marketplace.
Sketchfab - Sketchfab is an industrial design software tool is useful for ideation and for beginners in the industrial design field.
Characterz - Biggest diverse mix and match 3D illustration library