Ruby on Rails
API docs

Primary Source

http://rails.rubyonrails.com

Secondary Interfaces

http://www.noobkit.com—full search, links, comments, Ruby core and other Gems.
http://railsbrain.com—Rails API with AJAX flavor.
http://raildock.mytechsupport.com/—searchable API docs
http://omara.ca/rails—an alternate layout with a basic search

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Maybe some API docs with hyperlinks? You know, to other parts of the API docs?