Not that long ago, it took a little prowess to jailbreak, or unlock from Apple’s grip, an iPhone. But over time, it became more and more easy, now, all you have to do to jailbreak the iPhone 4 — just visit http://www.jailbreakme.com.
The browser based installation tool will allow you to enjoy the freedom of loading apps that Apple wouldn’t approve, apps that make your phone things do that they may not want you to as well. But heck, it’s your phone, and you should be able to do what you want with it.
And the Library of Congress agrees. It’s easier than ever before, and reportedly also works on the iPad, running iOS 4. So just do it!