The Economics Network are the latest organisation to take the plunge and get themselves a YouTube channel. They have made available a keynote from the recent DEE conference, from the Undercover Economist, Tim Harford.
The full abstract is available from their website, but I can thoroughly recommend watching Harford perform as he takes a gallop through a whole range of economic topics and some which you might not think were economic topics. He starts off by seeing if economic principles can be applied to dating.
The Economics Network also has a back catalogue of films produced by economics students as part of their Why Study Economics initiative.