Python Comet Server
Orbited seems as a nice solution. Haven't tried it though.
Update: things have changed in the last 2.5 years.
We now have websockets in all major browsers, except IE (naturally) and a couple of very good abstractions over it, that provide many methods of emulating real-time communication.
- socket.io along with tornadio (socket.io 0.6) and tornadio2 (socket.io 0.7+)
- sock.js along with SockJS-tornado
I recommend you should use StreamHub Comet Server - its used by a lot of people - personally I use it with a couple of Django sites I run. You will need to write a tiny bit of Java to handle the streaming - I did this using Jython. The front-end code is some real simple Javascript a la:
StreamHub hub = new StreamHub();
hub.connect("http://myserver.com/");
hub.subscribe("newsfeed", function(sTopic, oData) { alert("new news item: " + oData.Title); });
The documentation is pretty good - I had similar problems as you trying to get started with the sparse docs of Cometd et al. For a start I'd read Getting Started With Comet and StreamHub, download and see how some of the examples work and reference the API docs if you need to:
- Javascript API JSDoc
- Streaming from Java Javadoc