Tetrisly - Starter kit for design systems and wireframes builder (Sketch/Figma)
Uppy - The next open source file uploader for web browsers
Material Design Kit - Design for Android better and faster
Filestack - Simple file uploader and robust APIs for uploading, transforming, and delivering any file into your app. Filestack is a collection of tools and powerful APIs that make it simple to upload, transform, and deliver content.
React Rainbow Components - Build your web application in a snap.
Uploadcare - File uploading, media processing & content delivery for modern web apps