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 Visualizer - Enter user/repo and see the project visually
Sourcetrail - Sourcetrail is a cross-platform source explorer for C/C++ and Java.
Gource - Gource is a software version control visualization tool.
PhpMetrics - PhpMetrics provides metrics about PHP project and classes, with beautiful and readable HTML report.
SyntaxDB - Easily look up programming syntax for multiple languages