LaunchKit - Open Source - A popular suite of developer tools, now 100% open source.
Microlink - Extract structured data from any website
whatdevsneed - This is whatdevsneed.
CRX Extractor - Get any Chrome Extension source code. Learn and hack!
SmallDevTools - Handy developer tools with a delightful interface
Parsers - Parsers is a platform for extracting unstructured data from sites and their visualization without code.