Flaticon is a largest database for icons. You can find variety of icons, Interface icons, Animated icons and stickers here and can be downloaded freely in multiple formats such as PNG, SVG, EPS, PSD and CSS. You can also edit existing icons using Adobe After Effect.
Omatsuri is an open-source web application that provides 12 different tools for developers. Its like 'All in one' app.
RapidAPI is the largest API hub. It offers a vast collection of APIs across various categories such as weather, social media, e-commerce, finance, and more. You can easily search and integrate the API in your application. Here not all API keys are free, the site provides both free as well as paid subscription. For some api keys you need to pay in-order to use and integrate them in your application.
Storyset platform provides you awesome free customizable illustrations to use in your project. With Storyset, you can easily customize, animate, and download illustrations to create beautiful application especially landing pages. It also provides option to edit the illustrations and downloading in PNG and SVG formats.