Cowboy is a small, fast, modular HTTP server written in Erlang.
Express is a web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.
Heroku is a cloud platform as a service (PaaS) supporting several programming languages.
Mailchimp is a marketing automation platform and email marketing service.
Twitter is a 'microblogging' system that allows you to send and receive short posts called tweets.