Icons8 - Free app for Mac & Windows already containing 39,800 icons. Allows to search and import icons…
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Feather Icons - Simply beautiful open source icons
SVGeezy - Allows for automatic Image fallbacks for browsers that can't handle SVGs.
Flaticon - A database of free vector icons.
IcoMoon - IcoMoon is an icon management tool that is build to provide iconography.