Bibliomani – Read, study and research literature, thousands of e-books, poems, articles, short stories and plays.
CIA World Factbook – The “CIA World Factbook” from the Central Intelligence Agency contains basic facts on all the countries of the world; however, the most recent data for some statistics may be out of date.
Connexions – At Connexions you can view and share educational material made of modules that can be organized as courses, reports, books, etc. Collaborate. Check licenses.
Eldritch Press – Here are 20,000 free books that have been dedicated to the public domain.
Eric S Raymond’s Page – Various open source documents and software. Have to search for the gems.
ERICDigests.org – A way to access the ERIC Digests (public domain education articles) produced by the former ERIC Clearinghouse system.
Free Government Information – Government information portal (drill down).
Gutenberg.org – Over 30,000 free books are in this project’s online catalog. They have over 100,000 books at Project Gutenberg. You may download and redistribute these books.
Google Books – Fiction and non-fiction books.
Government Reports – Noteworthy government reports covering a broad spectrum of topics including crime, education, employment, energy, health and family, amongst others.
Health Research Books – The worlds largest publisher of rare and unusual books with thousands of titles and hundreds of unique categories.
ibiblio – Ibiblio is a public library and digital archive and is home to one of the largest free online information databases.
Kids.gov – Kids, teens, toddlers, parenting, etc. The U S Government’s Official Web Portal for kids.
Massachusetts Institute of Technology – You can’t use this info for commercial purposes, but if you’re offering a free report to your readers, this info may come in handy.
Planet PDF – Literature Classics in PDF.
Publications.usa.gov – Reports & publications on just about anything from the Federal Citizen Information Center.
The Library of Congress Country Studies – Information on over 100 countries in the world. Some of this material is not kept up to date.
The Online Books Page – According to them they listing over 1 million free books on the Web.
University of Virginia Library EText Center – Electronic Text Center. An Internet-accessible collection of documents central to teaching and research in the humanities.
US Army Chaplain Center – The US Army Chaplain Center and School has several PD publications that you can use.
USA Government Topics Portal – U.S government information by topic.
USGS Geography Publications – Fact sheets, booklets, leaflets, bulletins, product lists and educational material galore!
USGS Publications Warehouse– Search over 100,000 publications written by USGS scientists!
Wikipedia Public Domain References – Wikipedia Public Domain Directories.