Travis CI (https://travis-ci.org/) is an open source hosted PaaS solution for CI/CD. It is free for public/OSS projects and needs a subscription for use by private/enterprise projects. It supports applications written in a variety of languages and platforms and is heavily used by open source projects, including JHipster, for their CI needs. It has excellent integration with version control tools and offers an enterprise version as well. It is very easy to set up and use and has a simple YAML-based configuration. Advanced setups are typically done using shell scripts that can be triggered by the YAML configuration using hooks.