searchcode - A source code search engine
Insight.io - Best web-based IDE-like source code browsing and search tool
CRX Extractor - Get any Chrome Extension source code. Learn and hack!
Krugle - Krugle is the complete enterprise solution for search targeted to the development organization.
Relevance - No code interface to customize search rankings
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+.