Gooru Learning

"Gooru is a search engine for learning that allows you to explore and study over 2,600 standards-aligned and personalized study guides. Study guides cover 5th-12th grade math and science topics, and resources include digital textbooks, animations, instructor videos and more. All resources are vetted and organized by teachers or Gooru’s content experts, so you don’t have to sort through the mess of subpar educational resources available online yourself.
Gooru also makes it easy for you to connect with your worldwide peers to make learning a social experience. Post questions to an active community of students, teachers and experts, or find friends and peers to study with.

Gooru adapts to you. Based on the topics you study and your performance on self-assessments, Gooru suggests resources and study guides that will help you master the concepts. You can track your study habits and monitor your performance on any of the topics you study." 

I registered to have a look around and, at the moment, there are tons of resources for Math and Science only. The resources I dipped into were high quality and clearly marked as 'learner' or 'teacher' audience. A great resource for promoting independent learning, supplementing teaching as well as being a source of lesson plans and ideas.