I found a very funny and informative series of videos on YouTube that go over some important electronics principles.
Here is the PWM video:
http://www.youtube.com/watch?v=Lf7JJAAZxEU
Here is a playlist of videos by the same guy where he goes over some important electronic hardware like diodes, resistors and transistors.
http://www.youtube.com/watch?v=-mHLvtGjum4&feature=list_related&playnext=1&list=SP 970BF3F6D77B12E8
Here is another playlist by the same guy:
http://www.youtube.com/watch?v=aOJuCYgmPPE&list=PLDE23FAC8A681FA46&featur e=plpp_play_all
I really enjoined these videos and I think you guys will too.