Space Icons - 77 hand-drawn space icons in multiple graphic versions
Feather Icons - Simply beautiful open source icons
IconStore - Free icon packs by first-class designers
Icons8 - Free app for Mac & Windows already containing 39,800 icons. Allows to search and import icons…
Iconjar - Store all your icons in one place, just a click away
Material Design Icons - 750 Free open-source glyphs by Google