The Public Domain by James Boyle, looks to be an interesting new publication, billed as "introducing readers to the idea of the public domain and describes how it is being tragically eroded by our current copyright, patent, and trademark laws." - In many ways, a call to arms for people to use the Creative Commons, the licensing system which you already use when either selling or giving away your .eps product plans on Ponoko.
Boyle's book is available to buy physically, or to download for free as a .pdf, or indeed read online for free through the publishers' (Yale University Press) website. I have started to read the book by the latter method and found the website very lucid and usable and the writing clear and straight forward. I particularly like Boyle's point in the preface on the accessibility of this area of thought:
"Contrary to what everyone has told you, the subject of intellectual property is both accessible and interesting; what people can understand, they can change—or pressure their legislators to change… Every news story refers to intellectual property as "arcane," "technical," or "abstruse" in the same way as they referred to former attorney general Alberto Gonzales as "controversial." It is a verbal tic and it serves to reinforce the idea that this is something about which popular debate is impossible. But it is also wrong."
Boyle also writes on the Public Domain website about the benefits of simultaneously selling your book and giving it away. There's a cracking video from Creative Commons at the bottom of that page, which makes a great introduction for those of us new to the concept.