Flaticon - A database of free vector 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!
Icon Shop - Get beautiful premium quality vector icons
Fontello - Tool to build custom fonts with icons.
Iconfinder - Iconfinder is the leading search engine and market place for vector icons in SVG, PNG, CSH and AI format..
Line Awesome - Same icons as Font Awesome, but in a modern outline style.