Academic Earth is a site similar to Einztein. It is a collection of links to free online courses from a variety of schools and web sites.
You can search for courses by subject, university, or instructor. Subjects include Astronomy, Biology, Business, Chemistry, Education, Engineering, Law, Math, Physics, Psychology and much more. Universities include Berkeley, Columbia, Harvard, MIT, NYU, Princeton, Yale and more.
This is a good resource for finding courses for yourself, brushing up on material, or having students use it as a supplemental classroom resource.