ok, i just had a look at the 12" Specification Sheet and it says:
Video and graphics support
Dual display and video mirroring: Simultaneously
supports up to 1024 by 768 pixels on the built-in
display and up to 1600 by 1200 pixels on an external
display, both at millions of colours
now i'm wondering if you can use any of the Apple Cinema Displays with the 12" PowerBook?