Creative Market - Buy and sell handcrafted, mousemade design content like vector patterns, icons, photoshop brushes, fonts and more at Creative Market.
Elements for Sketch - High-quality UI Kits in Sketch, for free
SocialSizes - Sketch templates for sharing images & videos on social media
Tailwind CSS - A utility-first CSS framework for rapidly building custom user interfaces.
Icons8 Developer API - 500k+ design assets, now available on-demand
DynaMaker - Cloud service for Visual Product Configuration with parametric geometry and CAD / BIM