I made this video to help some of the local hacker space people with understanding the how and why of the series resistor for LEDs. I hope it helps someone.
http://www.youtube.com/watch?v=B042Ow8hPdU
http://www.youtube.com/watch?v=B042Ow8hPdU
by Aaron Carman
by Aaron Carman
by Duane Benson
by Jake Hertz