You probably seen these around on websites, outside on various advertisements, packages, etc. They're everywhere. If you have an Android/iPhone/Blackberry phone with a camera and a browser with a data plan and/or WiFi, you can get a scanner to decrypt these codes. They're great for using as a vCard, give out phone numbers and text messages, wireless network info, URLs, events, etc. They're quite fun. Here's a link to create your own so you can rickroll strangers or post your website anywhere you want:
http://zxing.appspot.com/generator/
Example: This one links to the forums.
