IconStore - Free icon packs by first-class designers
App Icon Maker - Create icons for mobile app stores online for free.
Feather Icons - Simply beautiful open source icons
EasyAppIcon - EasyAppIcon helps you to create your own app icons easily. Supporting Android Adaptive Icon!
Iconjar - Store all your icons in one place, just a click away
MakeAppIcon - MakeAppIcon resizes and optimizes your icon designs into all formats needed for iOS and Android mobile app!