Bananas is a lightweight web framework built for JavaScript, focusing on simplicity and fast prototyping of web applications. Because there are no servers involved (except for the stun, turn and signaling servers that are needed for exchanging the initial connection information), you need to have a way to communicate the url to the person you're sharing your screen with.
JetClass, Java net-class application, allows virtual lectures to be held by teachers and students located in front of their computers, somewhere around the globe. It's written in Pure Java, relying on CORBA for network communications.