A Physics Classroom resource. The Physics Classroom was written and developed by Tom Henderson, a teacher of chemistry at Glenbrook South High School in Glenview, Illinois since 1989. "The Physics Classroom is an online, free to use physics website developed primarily for beginning physics students and their teachers. The website features a variety of sections intended to support both teachers and students in the tasks of learning and teaching physics." --website.
An Annenberg Learner resource, this is "an on-line course that explores the frontiers of physics. The 11 units, accompanied by videos, interactive simulations, and a comprehensive Facilitator's Guide, work together to present an overview of key areas of rapidly-advancing knowledge in the field, arranged from the sub-atomic scale to the cosmological." -- Website