Great start so far! I'm relatively new to the subject (but not to math), but have recently been reading Spivak's "Catetory Theory for the Science" with a group via http://cat.boffosocko.com. I like the general overview of the subject along with some more detailed examples (doing them in green is a great idea) that look ahead a bit to where you're going. Using a recurring music example will be useful I think and broaden the audience to those outside of computer science. Looking forward to watching the rest of the series.