Recently a big step towards electronics printing occurred. Xerox has invented a new type of "Silver Ink", purportedly for 2D inkjet-style printing. However, we suspect this might also be ideal for 3D printers. Imagine an Objet printer (capable of handling two different print materials simultaneously) loaded with plastic and "silver ink". You could theoretically print objects with embedded (albeit simple) electronics. Well, wiring at least.
Via PhysOrg (Hat tip to Micah)