Gooru is a site I wrote about a while back when it was in Alpha status. It is now in Beta status and open for everyone to use.
Gooru describes itself as a "Search Engine for Learning". It is a study tool that allows students to explore resources and study guides that are aligned to standards. The materials are in math, social studeis and science and are from 5th grade up to high school. Resources include digital textbooks, videos, animations, links and much more. It also includes social media functions so that students can work, study, and share with others.There are ready made collections of resources, and users can create their own collections of resources as a study tool, or even as a class project.
There are self-assessments in Gooru that help it adapt to the student, suggesting resources and study guides based on the student's performance.
The resources are all vetted by educational professionals and you can even create custom collections and resources.
The site has resources to learn more about it and how it can be beneficial to educators and students.