Schoology is a free course management system for educators that allows them to manage their lessons, post resources and assignments, create quizzes, link to additional resources, conduct online courses, provide one-on-one help sessions and host discussions.
It allows educators to connect and engage their students, parents, and other educators. You can create lessons with a variety of media and content, organize them as needed,
You can connect and import from Google Docs, Khan Academy, Blackboard, Moodle and Examview so you can use all these resources in your Schoology account. You can also create online discussions, link to other resources, search for resources other teachers have posted, create and automatically assess online quizzes and track user data.
It's a very powerful tool that can help teachers create and organize lesson materials and connect with their students.
There is a premium version for schools and districts that adds additional enterprise type features.
Related services: Blackboard, Edmodo, Moodle, My Big Campus, it's Learning, CourseKit, and LearnBoost.