Physics
Physics.org [w]
Large search engine of physics-related sites and resources.
Link Type: redirected
Cost? Free
Submission info: here
PhysicsWeb Resources [w]
Directory of reference sources, organizations, education resources, publications etc.
Link Type: redirected
Cost? Free
How to submit: You'll need to register for an account before you can add a resource.
If any of the above information is incorrect, or you know of other quality resources that should be listed here, please get in touch.