I'll list non-profit or commercial-free sources. I evaluate resources based on who is providing the digital content/source and their motive and what it entails and who is it aimed for. I view it as research/digital library skills, but then again I have a library degree (not a physics degree!) smile.

http://watchknowlearn.org/default.aspx - provides free educational videos for ages 3-18. They're indexed and categorized by age, topic. By contrast to Khan Academy, they may not be as good in advanced or aimed at higher levels of physics.

http://www.goodsitesforkids.org/ - is aimed at kids and is comprehensive. If you use the enter physics in the Google search engine under list of topics, you'll get the links specific to it.

http://librarianchick.com/mediawiki/index.php?title=Main_Page - has a section on science for free or open source materials, classes, etc. - aimed at kids and teens.

http://sourceforge.net/ - find, publish, or create open software for free - has a section on physics under their science/engineering side list.

http://www.opensourcephysics.org/ - open source physics. This one might be aimed at college students though and goes into various fields of physics.