Oh, I know how much you want this!
In the long tradition of putting the words “intern” and “coffee” together, our summer intern extraordinaire, @mmcnierney, released api-sandbox, an open-source JQuery plugin written in Coffeescript (get it?), that allows web apps to easily implement sandbox environments for an API explorer. API Sandbox is just the first part of an API explorer Matt will be releasing over the next couple of weeks, so get excited!
Read his post for details.