BrightStorm: BrightStorm currently targets high-school aged students with videos of great teachers presenting the content. Their more than 2500 math and science videos are free.
Gooru: Just launched in beta, Gooru Learning is a "search engine for learning" that harnesses the power of the web by organizing free, online education resources into searchable collections, accessible from any web or mobile platform. Using machine learning and human judgment, Gooru curates, auto-tags and contextualizes collections of web resources to accommodate personalized learning pathways. Gooru collections are aligned to US Common Core Standards for Math and to California Science Curriculum Standards.
"MIT+K12 is an initiative of the Massachusetts Institute of Technology to harness the creativity of MIT's most outstanding asset -- its students -- in bringing excitement and understanding of science, technology, engineering, and math to kids."
The Futures Channel: Based on the goal of using new media technologies to create a channel between scientists, enginners, explorers, visionaries and learners, The Future Channel partners with schools to provide these high-quality digital learning resources.
LearnersTV: This site provides free video and audio lectures of whole courses conducted by faculty from reputed universities around the world across many fields.
Discovery Education: This site offers award-winning, standard-aligned digital content, interactive lessons and virtual experiences that aim to be immersive and engaging for students.
Backpack TV: Backpack.tv pulls from various sources to create a highly curated library of education videos organized by academic subject and detailed topic. Many of the videos are linked to topics from popular textbooks, a real bonus for finding just the right video. Videos can be user-rated.