GitHub Visualizer - Enter user/repo and see the project visually
Sourcegraph - Sourcegraph is a free, self-hosted code search and intelligence server that helps developers find, review, understand, and debug code. Use it with any Git code host for teams from 1 to 10,000+.
CodeFlower - CodeFlower visualizes source code repositories using an interactive tree.
Atlassian Fisheye - With FishEye you can search code, visualize and report on activity and find for commits, files, revisions, or teammates across SVN, Git, Mercurial, CVS and Perforce.
Codeology - Open-source algorithm that visualizes GitHub projects
Krugle - Krugle is the complete enterprise solution for search targeted to the development organization.