Check out Codeacademy.com. Once you land on the page, your first lesson is waiting for you. No signup required. But once you do sign up (which is free), you can track your progress.
As someone who has used many online tutorials, Codeacademy's simplicity keeps the lessons clear, which is important when trying to take in the concepts of any programming language.
Apparently, the site was begun only a little more than a week ago, and isn't necessarily finished. But it got a lot of attention quickly because of its simple, intuitive and clear approach to teaching the material.