buildzion.com

Nature (the popular PBS series)
www.pbs.org/wnet/nature/category/video/watch-full-episodes
Iris (from BYUtv)
www.byutv.org/show/1794
Nova
video.pbs.org/program/979359664/
Scientific American (with hulu ads)
hulu.com/scientific-american-frontiers
Science.discovery.com:
How its made
How do they do it        
Deconstructed (How it works)
Cosmos
More How it works
neok12-how it works 
sciencehack.com - also has many other science videos
Discovery - Education
streaming.discoveryeducation.com
Academic Earth (College Lectures)
www.academicearth.org 
Math at Khan Academy
khanacademy.org
Educational Children's Videos by subject:
neok12.com
video.about.com
Educational
Origami   
Family Crafts