1. Search, track, and visualize code changes

  2. Hound is an extremely fast source code search engine. 

  3. OpenGrok is a fast and usable source code search and cross reference engine.

  4. Lightning fast code searching made easy

  5. Zoekt is a text search engine, intended for use with source code.

  6. zGrepCode.com is your helper to browse open source code online.

  7. Codase is the leading source code search company with advanced source code understanding and xml...

  8. Java examples in open source code.

  9. Snip2Code is a free service that lets users search, share and collect code snippets, the basic...

  10. 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+.

  11. 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.

  12. Krugle is the complete enterprise solution for search targeted to the development organization.