Potto Project - Open Engineering Textbooks
URL = http://www.potto.org/
"The Potto Project was started by Dr. Genick Bar-Meir to produce and distribute high quality open textbooks. Books are made available in pdf, LaTeX, dvi and postscript under the GFDL. So far the main books are ‘Fundamentals of Compressible Flow’ and ‘Fundamentals of Die Casting Design’, both available from the downloads page."