Below is a list of sites that give you free online videos for your various subjects in school to engineering to economics. I have listed them below, in order of simplicity (i have felt).
KhanAcademy is a newer one with a tweet from Bill Gates himself a few days back !
http://www.khanacademy.org/
http://academicearth.org/
http://learnerstv.com/
http://ocw.mit.edu/index.htm
