National Academies Press Makes its Reports Freely Available

"... Effective June 2nd, PDFs of reports that are currently for sale on the National Academies Press (NAP) Website and PDFs associated with future reports ... will be offered free of charge to all Web visitors. ..."

http://notes.nap.edu/2011/06/02/more-than-4000-national-academies-press-pdfs-now-available-to-download-for-free