Josh Kopel has written a detailed series of articles on using DC motors pulled from inkjet printers. They can be used as servos, as they often have optical encoders attached due to the original purpose of the motors - to move and track the motion of print heads and paper through the printer. Therefore by using the encoder you can create a servo-like device with reasonable success. Watch the following video for a quick demonstration:
If you find success with one then all those cheap inkjet printers may have a second life once the ink runs out. So to get started head over to Josh's project pages here. And we're on twitter and Google+, so follow us for news and product updates as well.