Physics and astronomy are two very closely related branches of science.
The fundamentals of physics are used to explain astronomical phenomena and develop technologies that will help us understand more.
Here is a selection of some recommended Fundamental Physics sites.
Physlink.com - Physics and Astronomy Online: Includes current news on Physics and Astronomy, essays, archive of questions answered by experts, software reviews, important references (tables on constants, etc.), directories of journals, societies, publishers, institutes and labs, an online store and fun stuff.
Please feel free to share your favorite Astronomy Fundamental Physics websites (with a short description).