Radix Icons - A crisp set of 15×15 icons. Open source.
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.
Bjango App Icon Templates - App icon templates for PS, Ai, Sketch and Affinity Designer
Craftwork - A collection of User Interface resources made by Craftwork