..FWIW, for those of you who haven't been enlightened with the power that Google Apps Script[1] offers yet, be sure to check it out: http://script.google.com. Layered on top of Spreadsheets, this pair takes prototyping to a whole new level.
However I do enjoy the API. It's wonderful how easy it is to prototype an idea and get it off the ground with minimal effort.
My team is currently using it as a makeshift JSON level editor for a mobile game where each tab represents a collection of objects and the schema is defined dynamically by whatever is in the frozen header row. (think Backbone collections and models).
If someone is interested in a project, email is in my profile. I've gotten very lucky meeting smart people through HN before, so why not try again!