Greg Mankiw's assigned homework leaves me confident I'd pass introductory econ at Harvard.
More seriously, I've always found that the course materials provided online by MIT very useful in learning or gauging process. Bizarrely, I find their graduate micro I exam easier than their undergraduate intermediate micro.
NOTE: For some reason, blogger dates posts from the day I start them, not the day I finish them. No, I don't understand, either.