IconStore - Free icon packs by first-class designers
App Icon Maker - Create icons for mobile app stores online for free.
IconBros - Free and continuously growing high quality icons
EasyAppIcon - EasyAppIcon helps you to create your own app icons easily. Supporting Android Adaptive Icon!
Icons8 Apps - 1M+ professional icons, illustrations, and photos for web, Mac, Windows, and Linux
MakeAppIcon - MakeAppIcon resizes and optimizes your icon designs into all formats needed for iOS and Android mobile app!