An excellent resource for background information on physics.
The Physics Classroom is an excellent resource to supplement a physics classroom. It is simple and effective at providing the basics in physics.
How I Use It
I use the Physics Classroom as an online resource students can use to reinforce their understanding of physics concepts. It is a supplement to lecture notes and the textbook; a place students can turn to when they feel like they could use an explanation of a physics idea. I think it is a supplemental (free) resource that works.