Someone recently directed my attention to http://www.codecademy.com/.
It is a pretty neat service which aims to teach the visitors programming in a very intuitive and easy to grasp way. After a lot of struggling, I did manage to complete the first lesson ;-).
It was short, to the point and all in all, very well made. I had a look at their other lessons (there aren’t that many at the moment but you can sign up as a teacher and make your own ones!).
I really like this idea. Most schools have some sort of system for sending in labs or exercises and such. I see this service as a replacement for that. Maybe let the schools pay a small fee for some sort of premium account that gives them a the ability to create tests suites and other power user functions.
Right now, the lack of content is the biggest issue but like all of these web 3.0 applications, if you build a big enough user base, the content will come. I hope this takes off. I really do.