Filestack!

Uploadcare provides cloud storage, media uploading, image processing, and CDN for your website or app. Add media from your local storage, any URL, Facebook, Instagram, Dropbox, Google Drive, OneDrive, Evernote, and more. Upoadcare is highly optimized for adaptive web designs and reducing site loading times.

Transloadit handles file uploads, resize, crop and watermark your images, make GIFs, transcode your videos, extract thumbnails, generate audio waveforms, and so much more. In short, it is a Swiss Army Knife for your files and a one-stop place for developers that are looking to solve media processing.

Kloudless is a developer tool that allows developers to work with any storage service through a single, unified API.

Free customizable file browser and a self hosted node.js API server, to manage your users' cloud services from your application.

Cloud Explorer is a open-source S3 client. It works on Windows, Linux, and Mac. It has a graphical and command line interface for each supported operating system.

AssetPicker is a free asset or file picker designed to be easily included into web application interfaces. It has a file abstraction layer allowing adapters to connect to any remote storage, be it cloud storages like Amazon S3, Google Drive or Dropbox or assets from a custom web application server. In opposite to other file managers or pickers, AssetPicker is suitable for hierarchical as well as associative file storages.

Receive print jobs, photos, videos, graphics and other large files on your site. Just copy and paste some HTML to get an upload form that looks like your site. Setup email alerts, password protection and PayPal integration.