IconBros - Free and continuously growing high quality icons
App Icon Maker - Create icons for mobile app stores online for free.
IconStore - Free icon packs by first-class designers
MakeAppIcon - MakeAppIcon resizes and optimizes your icon designs into all formats needed for iOS and Android mobile app!
iOS Icons - The first marketplace for custom iOS icon packs
EasyAppIcon - EasyAppIcon helps you to create your own app icons easily. Supporting Android Adaptive Icon!