the variety of course available. Also love the step by step walkthrough of most course. Makes it easy to learn.

Virtual classes in Khan Academy are just so easy to follow. It makes you hungry to learn more and more. You basically can find any topic, at least i've never had any trouble in finding any topic i'd like to learn. After finishing a course it recommends you other courses so you can complement what you learned. Best of all, it is FREE.

I like the grammar videos because I teach English& the content applies to my field of study.