Brother has a new compact printer expected to be available in March of 2007. The portable printer is called the MPrint (MW-260) and is small enough to hold in your hand.
The A6 sized printer measures only 160mm x 210mm x 18.5mm and weighs only 500 grams. It can be connected to via IRDA, Bluetooth or USB and prints up to 20 A6 pages per minute at a 300×300 dpi resolution. The MPrint is also compatible with a PC, Pocket PC and Windows Mobile to make it a true mobile printing solution.
The MPrint is expected to be available in Japan only at this point, and a price has not yet been determined.
Translated Source [Brother Japan]