Feather Icons - Simply beautiful open source icons
The Noun Project - Creating, Sharing and Celebrating the World's Visual Language
IconStore - Free icon packs by first-class designers
Nucleo - Commercial vector icons and accompanying apps to manage and customize them.
IconBros - Free and continuously growing high quality icons
Font Awesome - Font Awesome makes it easy to add vector icons and social logos to your website. And version 5 is redesigned and built from the ground up!