A library of over 2,600 videos (covering everything from arithmetic to physics, finance, and history) and 235 practice exercises.
Khan Academy’s popularity continues and it makes a significant jump up the list this year – of 15 places.
Comments from some of those who selected Khan Academy as one of their top tools
The analytics alone are worth the time to use this site, 2014
Use these video lessons to help me flip my own classroom, 2013
Independent learning for students, 2013