The National Academies Press is the publishing arm of the National Academies and publishes reports from the National Academy of Sciences, National Academy of Engineering, the Institute of Medicine and the National Research Council. There are over 200 books per year published a topics ranging from science to engineering and health and even Education.
There is currently over 4000 titles available in PDF format and they can now all be downloaded for free, either by chapter or by entire book.
There are some great reports and books on science, education, computers, earth science, health and medicine, security, environmental, and much more.
You do have to create a free account if you are going to do lots of downloading, but you can continue as a guest also.
This is a great resource for teachers and students looking for research and reports on different topics.
Here's a listing of all of the sub-categories in Education: