CodeSandbox is genuinely amazing. It brings the power of the text editor and development of web applications to the web and does it well. You can write out and deploy a web app right from the browser.
Announcing CodeSandbox 2.5 - Many features added.
CodeSandbox CI 101 - Describes what CodeSandbox CI is, how it will benefit you as a library maintainer, and how to set it up for your library.
Codesandboxer - Deploy any component directly to codesandbox from anywhere.
GitHubBox - Open any GitHub repo in CodeSandbox by changing the hostname.