i saw an article on boingboing about mini usb monitors, and am now wanting one very much! the mimo 740 (above) has built in microphone and webcam, and is also touchscreen. the mimo range all come with adjustable stands, and can flp to be either portrait or landscape.
the main uses for a gadget like this would probably be for widgets, instant messaging or video messaging (skype maybe?), email, video (while you're doing other things), and photoshop or illustrator tools, which is probably what i would use it for most. this would give you the whole of your main monitor to concentrate on what you are working on, a problem when the screen is cluttered with lots of different tool boxes.
the screens range from $99 to $199, the price going up for the extras that the 740 includes (mic, webcam and touch). but the basic model (the 710, below) could still be very useful!
link to boingboing article
link to mimo product page