Stanford’s Coding Together Class

piazza.com:

Stanford’s iPhone and iPad Development class has had over 10 million downloads on iTunes U, making it one of the most popular online courses on earth. And it’s about to get better, because now you can do it with friends.
For the first time, Stanford’s most celebrated iTunes U course includes peer collaboration, so you can learn alongside fellow mobile developers from around the world. If you’ve tried it alone and gotten stuck, now there will be people to help. If you’ve taken it before and aced it, now you can sharpen your knowledge by helping others. And if you’ve been meaning to learn Apps for iPhone & iPad, there may never be a better time.