Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Krugle - Krugle is the complete enterprise solution for search targeted to the development organization.
GitZip - Download or create a download link for a GitHub project folder/sub-folder or file.
OpenGrok - OpenGrok is a fast and usable source code search and cross reference engine.
GitHub Hovercard - GitHub Hovercard provides neat hovercards for GitHub.
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+.