Khan Academy

http://www.khanacademy.org

i found this awesome website.

there is a lot of interesting videos

and also there is something call "try an exercise"

starting with simple addition , ending with trigonometry ,arithmetic and algebra challenges.

Probably easy stuff for a lot of LGplayers, but seems very didactic to me, and any one who is interested to learn.

Enjoy.

It is a really nice place to learn about a lot of different stuff. Can only give my thumbs up.

Similarly, Stanford has some online courses, e.g. Machine Learning and others listed on that page. I hear that MIT also has online courses, although I haven't taken any.

FWIW, http://www.udacity.com/ offers some free computer science classes.