The Harvard Book Store, located in Cambridge, MA, provides customers the opportunity to print out copies of their own books or previously published titles via its Espresso Book Machine. The machine, which has been nicknamed 'Paige M. Gutenborg,' is a digital press that prints from print-ready PDF copies of the book and can, reportedly, print a book in four minutes.
According to the Harvard Book Store site, the paperback books printed by the Espresso Book Machine are all library-quality, printed with acid-free ink. Because the machine offers such great printing quality, you wouldn't be able to tell a book printed via the Espresso Book Machine from a book printed through a major publishing house.
Further, there is no minimum requirement as to the number of books you need to print for any given order. This means self-publishers can print as many or as little copies as they need without having to shell out a ton of cash.