I only learned of Vi Hart and saw one of her short videos six months ago.  Hart calls herself a "mathemusician," and she is simply AMAZING!  I love watching the fast-paced video clips of her doodling in her notebook while talking-a-mile-a-minute.  She earned a degree in music but had never taken a college math course. You'd never know it as she embodies a wonderful mathematical curiosity and has plenty of math smarts. 

Just last week Hart announced that she'll be working full-time with Khan Academy to post weekly videos.  This seems like a marriage made in math-video-heaven.

I showed my geometry students Mobius Story: Wind and Mr. Ug after we'd worked with the Mobius strip earlier this school year.