IconStore - Free icon packs by first-class designers
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!
Feather Icons - Simply beautiful open source icons
Flaticon - A database of free vector icons.
Iconjar - Store all your icons in one place, just a click away
Fontello - Tool to build custom fonts with icons.