I was happy to stumble across the site wpseek.com, which works as an all things WordPress search engine.
What really impressed me though is their API, which let’s you do things like get specs on a specific function or a list of all WP functions.
For example using the following URL http://api.wpseek.com/?method=wordpress.getfunction&s=the_title will return a JSON object with the basic Codex info on the plugin.
I don’t see a way to get info like WP_Query, but this is still a cool resource if you’re trying to pull together some simple docs on the fly.
Thanks to Oliver Schlöbe for your great work!