Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.
PullReminders - Review and release pull requests faster with Slack reminders and metrics.
SonarQube - SonarQube, a core component of the Sonar solution, is an open source, self-managed tool that systematically helps developers and organizations deliver Clean Code.
GitHub Metrics - Customize your profile with various plugins and metrics
CodeClimate - Code Climate provides automated code review for your apps, letting you fix quality and security issues before they hit production. We check every commit, branch and pull request for changes in quality and potential vulnerabilities.
24 Pull Requests - 24 Pull Requests is a little project to promote open source collaboration during December.