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