Richard White has been working an AJAX based scaffold for Ruby on Rails. He recently released Version 2.2.0. He recently released Version 3.1.2 (oops :)).

Scaffolding is Rails way of simplifying CRUD (Create, Read, Update, Delete) of your model. Although, scaffolding won’t help you create model associations (you have to actually write ruby code for that), it gives you a quick jump start to get you up and running.

Check out the demo at ajaxscaffold.com to see AJAXCRUD.