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!
Humaaans - Mix-&-match illustrations of humans with a design library.
Flaticon - A database of free vector icons.
Control Illustrations - 108 free flat illustrations with customizable characters
Fontello - Tool to build custom fonts with icons.
Ouch! Illustrations by Icons8 - Professional, perfectly matching, and customizable illustrations for any designs