searchcode - A source code search engine
Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
CRX Extractor - Get any Chrome Extension source code. Learn and hack!
The Search - The all in one search engine for PH, DN, HN and GitHub ✊
Relevance - No code interface to customize search rankings
Autocomplete API - Optimize your search with suggested search query values