Pascal's Triangle and Binomial Coefficients: http://www.youtube.com/watch?v=OMr9ZF1jgNc
A Pretty Cool Video about the Fibonacci Sequence and Golden Ratio, related to nature, building, aesthetics, etc.
http://www.youtube.com/watch?v=2nAycC7sGVI
Check out this site (math doodles and more): http://www.youtube.com/user/Vihart
Great Patterns to learn math: http://www.youtube.com/user/MisterNumbers