http://classics.mit.edu/
Classic Greek, Roman and Eastern texts on the Internet.

http://www.utm.edu/research/iep/
Website of the Internet Encyclopedia of Philosophy, containing a comprehensive alphabetized list of philosophers and terms with extensive description.

www.coreknowledge.org
Core Knowledge Foundation, founded by E.D. Hirsch to promote the dissemination of a standard stock of knowledge to educators and parents.  Includes a "core knowledge sequence" and network of Core Knowledge Schools. 

http://www.nctt.net
National Center for Teaching Thinking.  Provides professional development to teachers in fostering higher-order thinking in students.