A web-based "instant" messaging system - not quite instant because there's a 1.5 second delay while checking for data, since browsers don't have push facilities to be told to retrieve data from the server.

This app requires registration, and from there you can add friends to talk to (assuming they're already registered). An upload function is available to share photos and files, which are then displayed in the page, as well as recent messages. The option to view the past week or day's worth of chat with one particular friend is available, along with email notifications.

It works by sending a request to the server to detect whether an update to a chat has been posted. If it has, the data is then retrieved and instantly animated into the chat window. It's really much more clever than I can put into words - give it a try!