I'd seen (and loved) the TED videos online, but I only found out about the local TEDx franchise about 9 months ago. (If you haven't heard about it, you can find out more info at http://www.ted.com/tedx.)
The attendees were all very special too and there was a great atmosphere at the event. Speakers and topics were very varied, but all thought-provoking.
I was lucky enough to be able to speak (video pending...) but my favourite thing was writing on the posters on the walls, made by the volunteers.