Free: All time
Khan Academy is a non-profit educational website that features thousands of educational resources, including a personalized learning dashboard, over 100,000 exercise problems, and over 4,000 micro lectures via video tutorials. The subjects covers anything from mathematics to history to cosmology. All these are free to access for anybody around the world that has internet connection. Time to brush up on your trigonometry?
Website: www.khanacademy.org
Photo credit: Khan Academy
Tags: Education
