Armin Ronacher just wrote an interesting blog post.

Obviel is a JavaScript based glue toolkit that lets you assemble web applications on the client side. It integrates with client-side template languages; by default, Obviel works with JSON-template, which also has server-side implementations (in Python and other languages). Obviel is one approach to do some of what Armin is talking about. I've used Obviel to build a number of web applications already, and am looking for more to work on.

Last time I spoke about Obviel on this blog it didn't have any live demos. Now it has a few. We're working on more.