Nucleo - Commercial vector icons and accompanying apps to manage and customize them.
Material Icons Library - Free collection of 1000+ icons for design
Vivid JS - A highly customizable, open source SVG icons library
Eva Icons - 480 Open Source icons for common actions & items
Line Awesome - Same icons as Font Awesome, but in a modern outline style.
Iconjar - Store all your icons in one place, just a click away