Check out http://json.us.
It's an unannounced open JSON encoding
proxy intended for use with dynamically created script tags. There is
a drop-in replacement for XMLHttpRequest using this technique you may
also find useful.
JSON.us attempts to make cross-site scripting safe by doing things
like removing cookies, caching requests, providing identification info
to the end server and limiting where requests can go. Right now
JSON.us will proxy any of the sites on the big web 2.0 list at
The idea here is to make it possible to create entirely client-side
mash ups without having to put together your own proxy. Eventually
should such a thing catch on, sites would start to provide their own
JSON feeds, and the proxy would become uneccesary.
Let me know what you think.