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+.
DXR - Powerful code search for large codebases.
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.
Insight.io - Best web-based IDE-like source code browsing and search tool
Text Sherlock - Provides a fast, easy to install and use search engine for text but, mostly for source code.
CodeNavigator - CodeNavigator is a developer's tool for browsing source code using CScope.