AAPT (American Association of Physics Teachers). Meetings and resources for teachers and professors.
List of APS alliances of physicists and teachers, by state.
CPEP (Contemporary Physics Education Project), a non-profit group of educators and physicists that develops educational materials on modern physics.
NSTA (National Science Teachers Association), science education for K-12.
PAEMST (Presidential Award for Excellence in Math and Science Teaching) . List of the one science and one math teacher per state each year who have received this award.
CSTA (California Science Teachers Association). Resources, conferences.
CTA (California Teachers Association).
Other Physics Organizations
APS (American Physical Society). Many journals, news, resources, ...
Physics Central, for the general public.
AIP (American Institute of Physics). Physics societies, journals, history, ...
AAAS (American Association for the Advancement of Science), a nonprofit for professionals and the public.
ASP (Astronomical Society of the Pacific), large astronomical society of amateurs and professionals. Magazine, lectures, catalog.
Society for Amateur Scientists. Info, research, and resources for the amateur scientist. Also, index of Amateur Scientist columns from Scientific American.
NAS (The National Academies of Science), "advisors to the nation".