Uppy - The next open source file uploader for web browsers
AssetPicker - A free, easy to use, cross plattform ready asset or file picker.
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.
CDNify - Accelerate your apps and websites with the CDNify content delivery network. Superfast, simplified and affordable CDN for developers, startups and agencies.
Uppy.io - Next open source file uploader for web browsers
CarrierWave - Solution for file uploads for Rails, Sinatra and other Ruby web frameworks.