Asynchronous Servlets (introduced in Servlet 3.0) and Comet Servlet
In this meeting Shachar will discuss the new feature in Servlet 3.0 API: asynchronous request handling. This technique is useful when the delay between request and response is very long, and its impractical to hold thread as old Servlet API required. Also useful for server-initiated communication, when it's impractical to send requests every now and then, hoping that something changed on Server. With Comet, the server can push a notification to the client side only when something happens.
IMHO, it is important to become familiar with this, because it can save a project from awful work-arounds. So you all members of Java group are invited to sign up and participate.