Reference
OnlineCourses.com aggregates over 500 open college courses offered by institutions such as Yale, Harvard, Princeton, and MIT, providing a single platform you can search, and also allowing you to keep track of your progress and share it.
A list of 100 blogs by and for post-graduate students (covering a wide range of topics)
A new German initiative sounds intriguing: iVersity describes itself as a "collaboration network for academia." Available in English, German, Spanish and Portuguese, iVersity lets professors create research groups, conferences, and courses.
There's over 1500 video lectures available on a whole range of subjects at Academic Earth
https://academicearth.org/
Annenburg Learner has teacher resources and professional development across the curriculum, in the form of videos
The WWW Virtual Library is a good starting point for hunting up reference and subject sites:
http://vlib.org/
All Academic is an academic index for articles that are free online.
http://www.allacademic.com/
A relatively complete index of psychologically related electronic journals, conference proceedings, and other periodicals is available at:
https://psych.hanover.edu/Krantz/journal.html#j
If you're looking for old books (before around 1923), take at look at Project Gutenberg:
https://www.gutenberg.org/
Subject-directories
Architecture
Education
What Works Clearinghouse "reviews the research on the different programs, products, practices, and policies in education. Then, by focusing on the results from high-quality research, we try to answer the question “What works in education?” Our goal is to provide educators with the information they need to make evidence-based decisions."
Blog on online learning research
the National Center for Case Study Teaching in Science has nearly 400 case studies, plus articles for teachers on using the case study method for teaching science http://sciencecases.lib.buffalo.edu/cs/
Psychology
Sociology
Those who want a taste of sociology might like to check out the Everyday Sociology Blog, “a site that features interesting, informative, and most of all entertaining commentary from sociologists around the United States.“ Includes some interesting short videos.