Hi, I just found an interesting demo of what can be done with the cappuccino framework;
Push with Cappuccino and Tornado
As far as I understands it, It keeps an async client/server connection, which is great to keep a "content" updated.
I would like to know if there is any way I can do the same thing using JQuery or another library. Cappuccino looks a bit like a all-or-nothing framework.
What you are seeing there is not particular to cappucino or Tornado: its an example of HTTP long-polling to simulate async connections. Essentailly a client makes a request to the server with a very long (or infinite) timeout and the server responds when it has some data.
It's a workaround for the fact that until very recently there was no way for a browser to receive a request from a web-server. This is changing as the most recent web-standards are gaining adoption.
In short, there is nothing to stop you employing this kind of technique in any framework. Take a look at the wikipedia page on Comet for more info.
In your specific case, you might find the answers on this question helpful as they are specific to jQuery.