I knew mit opencouseware years ago. I always want to follow the fabulous courses but I was lazy. Recently, when I tried to find out some online courses to strengthen my background, I found the online courses are very costly. Therefore,the free courses from MIT are comparatively better resource, absolutely not pricey. Courses are offered from many departments. I am like a little kid in a candy store the first time, feeling excited and kinda of lost. Too many choices and every one of them is good.