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!
Nucleo - Commercial vector icons and accompanying apps to manage and customize them.
1000 Detailed Creative Icons - Carefully designed icons with tons of fine details
Vivid JS - A highly customizable, open source SVG icons library
Icons Mind - The Biggest iOS 8, iOS 7 & Android Icons Pack
Line Awesome - Same icons as Font Awesome, but in a modern outline style.