Michael Feichtinger has as recent post to his blog talking about HTML5 WebSockets including an example he's created.

HTML5 WebSockets makes it possible to open a persistent connection to a server within a web-browser via javascript. Websockets works already in the latest Webkit-browsers like Safari 5 and Chrome 5. Firefox 4 Beta 1 knows the Websocket-Object but it can't open the connection.

His sample script lets you control the cursors of the other visitors of the page via some Javascript that runs a "mousemove" event on the current page. You can get the source for both the WebSocketServer and server.