Start here for some simple example apps. There are a lot of different options to start with to learn the ways of using PubNub. If you have any questions please email help@pubnub.com for more details.
Make sure to visit the Simple Chat App as a good starting places.
This is a fun little dot tracker that is a shared resource between multiple browser windows. Try it with two separate browser windows.
Stalker is pretty neat and also intrusive. I recommend checking out this simple JS include. What is does is it will allow you to Follow anyone as they browse a website. It shows you what they SEE as the Scroll and Change Pages.