I wrote the plugin mentioned by Till. The plugin is an implementation of the Bayeux protocol and currently supports long-polling (local server via AJAX) and callback-polling (remote server via XSS). There is a Bayeux implementation for Python called cometd-twisted that I have heard my plugin works with, but I have not verified this. I have tested and verified it works with cometd-jetty and erlycomet which has a jQuery Comet example included. There is more info on my blog and the current code with a basic chat example can be found on its google code page. Hope this info is helpful and feel free to contact me if need any further help with the plugin.