Icons8 - Free app for Mac & Windows already containing 39,800 icons. Allows to search and import icons…
MakeAppIcon - MakeAppIcon resizes and optimizes your icon designs into all formats needed for iOS and Android mobile app!
Iconscout - Design Resource Marketplace.
EasyAppIcon - EasyAppIcon helps you to create your own app icons easily. Supporting Android Adaptive Icon!
Craftwork - A collection of User Interface resources made by Craftwork
App Icon Maker - Create icons for mobile app stores online for free.