Dropzone.js makes it dead simple to add a drag-and-drop file uploader to any website, complete with previews of uploaded files.

Autopilot turns Twilio’s API into a drag & drop builder, empowering marketers to visually automate SMS marketing without having to ask a developer.

…and is actually really useful for Web developers wanting to implement drag and drop functionality in a quick and elegant way. You can get it on GitHub.