Like Duncan, I've also been messing around with JSON-RPC lately. I'm got most of a WSGI implementation done and a python client library done. I have an article describing the client code here.
For pythoneers, I've got a question: This code is largely based on xmlrpclib. It could easily be implemented as a subclass of xmlrpclib.ServerProxy (instead of just copying the code). So my question is should I subclass it? I'm not doing it right now, since I think it might actually diverge from the xmlrpc code at some point, and it also is a little easier to understand since all the code is in one single file (in my opinion). Opinions? Ideas? Thoughts?