While it's not the only resource of its kind, it does feature in-browser coding and feedback. You have to get through those exercises in order to continue. While I felt it was far from thorough (you can often ape the examples you've been shown without really understanding what you're doing), it's a nice way to get your feet wet by taking baby steps.

They also provide freebies/discounts, like free Peepcode screencasts, discounts on Michael Hartl's screencasts, etc (varies by course). I personally feel it gives me its $25 (often $20 - you get $5 vouchers for courses you complete) value.