Marcel, Roy and I did a Geeknight session last week on building cross-platform apps using C#. We had a full room with more than 400 people checking out or handy work.
It was a blast doing it and we got really lucky with someone in the audience that took the trouble of filming us talking iPhone, Android and Windows Phone 7 development.
Thanks Tony Thijs for filming the whole thing.
You can find the different parts of the presentation here: