Have you ever came across an app that keeps all your API docs in one place ? If the answer is No, meet Dash. An app which keeps all the documentation in one place. It downloads and keeps them up to date. It has support for almost all languages.
The interface is similar to Xcode documentation browser, so you will feel at home. You can add document sets from your local hard drive or download from provided locations such as Stackoverflow and other places. It will scan your HD when you open the app and keep everything tidy.
The best part is that, it integrates with apps on your Mac such as Xcode, Eclipse, Alfred and many others, so that you can directly browse the API docs from within that app.
It has another cool feature known as Snippets. You can store test snippets and abbreviations for later use. It's really handy as you don't have to remember large texts.
The app is basically free with an option of in-app purchase. You can use it free with full features, but it will nag you sometimes for payments if you don't pay.