This is, without a doubt, the coolest thing I've seen in a long time.
Here, you get to try your "hacking" skills. It's not traditional network intrusion, so you have no issue with overloading networks or doing anything illegal. The objective is to complete levels - starting at level 1, each page asks you for a password to get to the next page. Your objective? Discover the password, or skip the password and just discover the URL of the next page directly.
The first level is easy. It gets harder after that, requiring you to have knowledge, an eye for details, and the ability to use tools. Of course, don't think the same tricks will save you every time, or you'll find yourself good and duped.
Give it a try! I cleared the first four levels pretty quick - L5 will take some time, so it can wait for the weekend.
Quiet you, I have plenty of life!