I just use Dash (https://itunes.apple.com/us/app/dash/id458034879?ls=1&mt...), which by the way has become my most important tool. I use it a thousand times every day and it makes me so much more productive - no more Googling! Combined with a fast harddisk, a query never takes longer than a second to complete, for basically every language/framework I develop in (iOS, Android, Ruby, Rails, Ember.js, jQuery, CSS, HTML).
Now that I read it, I sound like an ad, but it's really that good :)
Seconded, love Dash! I used it for iOS exclusively until I found it it actually supports other languages and environments, like Clojure! Excellent tool!
Really great feature I recently found out about: type e.g. "android:" to only show Android docs. That's superuseful for people like me who rapidly switch between languages (e.g. jquery -> ember -> jquery -> css ->...).
Now that I read it, I sound like an ad, but it's really that good :)