Key tools
GitHub, GitLab
Jenkins - https://jenkins.io/
Travis CI - https://travis-ci.org/
Nexus repository - http://www.sonatype.org/nexus/
Docker Registry - https://docs.docker.com/registry/ - "server side application that stores and lets you distribute Docker images"
SonarQube - https://www.sonarqube.org/ - code quality monitor
Logs: Elk, Elasticsearch, Logstash, Kibana
Monitoring: OpenNMS, Icinga, Sensu, Graphite, Suzieq, Prometheus, Grafana
"Packer is a tool for creating machine and container images for multiple platforms from a single source configuration" - https://www.packer.io/
Bento - "Packer templates for building minimal Vagrant baseboxes" - http://chef.github.io/bento
Aptly, JFrog
Other tools worth mentioning
Chef
A framework for cloud and systems automation written in Ruby
Puppet
Configuration management framework written in Ruby
Links: home, docs, Puppet OpenStack guide
OneOps
DevOps suite from WalmartLabs
Links: about
Camunda
BPMN Workflow Engine - https://camunda.org/
Conductor
Workflow engine, part of Netflix OSS - https://netflix.github.io/conductor/