A Brief Introduction to Engineering Graphics by Durfee and Kowalewski (pdf)
Engineering Drawing by E. Blanco (pdf)
Overview of engineering drawing from Wikipedia (html)
Intro to Mechanical Engineering Drawing, a basic, 15 min video tutorial (YouTube)
Graphics course notes from University of Plymouth, Course Notes for DSGN131, accessed October, 2010. (pdf file)
Overview of Geometric Dimensioning and Tolerancing (GD&T) from Wikipedia (html)
Geometric Dimensioning and Tolerancing Tutorial from efunda (html)
Perspective drawing tutorial (html)
Sketching tutorials from MIT (html)
Notes on shading and shadows from "Rapid Viz" by Hanks and Belliston (pdf)
Two-point perspective tutorial (YouTube video)
Basics of hand lettering (pdf)