I just launched a university course yesterday called (naturally) Reinventing Project-Based Learning. We've had a wonderful start with deep discussion (why projects?) and happy tech adventuring (our own Ning and wiki).
I'm of a mind that people will best understand PBL by experiencing PBL so off we go on a learning adventure that starts with the study of postage stamps and dives straightaway into the ways we transmit ideas over a distance- we'll analyze systems, civics, history, communications, commerce, geography and more.
Think about it (students are)-- Where might a study of postage stamps lead us?