featuring Andreas Antonopoulos @aantonop
What is Ethereum?:
http://www.youtube.com/watch?v=Wv3gpfZ1IK4
What are smart contracts?:
http://www.youtube.com/watch?v=j2ePlk0rw4U
featuring Joris Bontje @mids106
Sub-currency:
http://www.youtube.com/watch?v=BSEJEanSvUU
Namecoin:
Explanation: https://www.youtube.com/watch?v=L3Ry7DUSJQc