Feather Icons - Simply beautiful open source icons
Creative Market - Buy and sell handcrafted, mousemade design content like vector patterns, icons, photoshop brushes, fonts and more at Creative Market.
IconStore - Free icon packs by first-class designers
SocialSizes - Sketch templates for sharing images & videos on social media
Fluent Icons by Icons8 - Colorful and stylish icons for your projects
Icons8 Developer API - 500k+ design assets, now available on-demand