Guys at [bildr] wrote a nice tutorial on how to control & use a thermal printer with Arduino.
Outputting data can be extremely useful, and typically when we look at doing this, it is either to the Arduino’s serial terminal, or to some sort of display. But what about making physical copies of the data? (…) If you dont know about thermal printers, they are most often the printers your store’s receipts are printed on. The reason for this is that they dont use ink, or use a cartridge of any sort. The paper it prints on turns black when heated. So this printer simply applies heat where another printer would apply ink.