Just sharing this if anyone hasn't got an email from DC yet.
They're doing a series of hangouts on getting to grips with HTML5 Banner creation:
You should see a series of events that you can join from HTML5 Immersion, How to QA, Hand Coding and Advanced GWD.
Google+ Page: https://www.google.com/+DoubleClickRichMediaTraining
YouTube Channel: https://www.youtube.com/channel/UC8aEkSJJF_21nKrpJUAAsbQ