Dash 2 (note: paid app) has just been released and it comes with a Alfred 2 Workflow. Dash lets users instantly search through documentation for 130+ APIs (ranging from HTML to Cocoa), for more information, check out Dash's webpage. All of the Dash-supported documentation sets are available for offline use.
You can get the Dash workflow by installing Dash and going to Preferences > Integration > Alfred.
Supported documentation as of the 2.0 release (documentation is constantly added so this list might go out of date): iOS, OS X, Man Pages, .NET Framework, ActionScript, Akka, Android, Angular.js, Ansible, Appcelerator Titanium, Arduino, Backbone.js, Bash, Boost, Bootstrap, Bourbon, C, C++, CakePHP, Cappuccino, Chai, Chef, Clojure, Cocos2D, Cocos2D-X, Cocos3D, CodeIgniter, CoffeeScript, ColdFusion, Common Lisp, Compass, Cordova, Corona, CSS, Django, Dojo Toolkit, Drupal, D3.js, Elixir, Emacs Lisp, Ember.js, Emmet.io, Erlang, Express.js, ExpressionEngine, ExtJS, Flask, Foundation (by Zurb), Git, GLib, Grails, Go, Groovy, Haml, Haskell, HTML, Jade, Java, JavaFX, JavaScript, Joomla, jQuery, jQuery Mobile, jQuery UI, Knockout.js, Kobold2D, Laravel, LaTeX, Less, Lua, Lo-Dash, Marionette.js, Meteor, MongoDB, Mono, MooTools, MySQL, Nginx, Node.js, Ocaml, OpenCV, OpenGL, Perl, PhoneGap, PHP, Play, PostgreSQL, Processing, Prototype.js, Puppet, Python, Qt, R, Redis, Ruby, Ruby on Rails, Sass, Scala, Sencha Touch, Smarty, Sparrow, Spring Framework, SproutCore, SQLite, Stylus, SVG, Symfony, Tcl/Tk, Twig, Twisted, TYPO3, Underscore.js, Unity 3D, Vagrant, Vim, VMware vSphere, WordPress, Xamarin, Xojo, XSLT, XUL, Yii, YUI, Zend Framework, Zepto.js.