I found this nice channel of the Massachusetts Institute of Technology, presenting educational material for free.
http://www.youtube.com/user/MIT
There are a wide category of courses included. Maybe you find a topic that always interested you but you didn’t find much info about it
I didn’t check all the courses (way too many of them^^) but I have to say, it seems mostly high quality to me (there was one video that seemed to have been uploaded in a bad way or something, which was really low quality, but all the rest was just fine) and the explanations are well understandable.