Introduction: 4.0 and 4.0.1 IOS Easy 2-Step Jailbreak for IPhone/iPod/iPad
This is the most simple jailbreak of all the firmwares.
2. Internet Access
Step 1: Jailbreak!
Simply navigate to www.jailbreakme.com on your iPhone, iPod Touch, or iPad. Slide to jailbreak, and you're done! This only works on iOS 4 and 4.0.1.