I'm taking the cryptography course by Pr. Dan Boneh, it is awesome, it is really engaging, deep enough and all the material is very well done. Moreover I just discovered the second part of this course has been announced and is scheduled for early 2013, so it's fabulous.

All I can say is that for this course I would even be willing to invest myself even more (both in time and money) at the level of requirement of a graduate course. I really would be interested in paying the standart fee and follow the same course than the stanford students follow and have a kind of official credit in reward.