Zeal - Zeal is an API Documentation Browser.
Snippely - Snippely is a basic text and code organizational tool.
DevDocs - Open source API documentation browser with instant fuzzy search, offline mode, keyboard shortcuts, and more
SnippetsLab - SnippetsLab is an easy-to-use snippets manager.
Dash for macOS - Dash is an API Documentation Browser and Code Snippet Manager. Dash searches offline documentation of 200+ APIs and stores snippets of code. You can also generate your own documentation sets.
Quiver - Quiver is a notebook built for programmers.