Ever seen one of these?

Ever wondered what it is?
Basically, it is a '2d bar code' and is usually representative of a URL but can be any text up to 250 characters.
Reading one of these codes using an Android device is easy:
1) Get the barcode scanner app, this one to be exact:
http://www.cyrket.com/package/com.google.zxing.client.android
2) Start up the app and optionally read the instructions - it's really quite simple though.
3) Start scanning. The application will detect QR Codes and show you the URL, you can then click it to open it in your Android browser! Or if it is an email, it'll kick off a compose email session. If it is just text, it'll just show it you.