Looks interesting. I like the interactive explanations of program
source code.
I don't know if any of you have come across crunchy? (http://
code.google.com/p/crunchy/)
It seems to be a way of building fully interactive Python tutorials
that run entirely within a browser window. I suspect that a lot of
work would be required to get the most out of it, but in the long term
this might be an interesting way of delivering teaching materials
online.