Sony PSP
I've got a PSP. My excuse for getting one is that it is a really great way of viewing images for work...
Here's a pic of my PSP with an image that we've been working on displayed on the screen.

I really should have cleaned it first - as my fingerprints are detracting from the quality of a fantastic LCD screen.
The LCD is 55x95mm which translates to 272x480 pixels and 16.7 million colours.
It will run slide presentations of any jpegs that are saved on to Memory Stick Duo media. It connects to your computer via a mini USB cable (not included).
These are due for release in the UK in September and will cost about 180 quid. Or you can go down Tottenham Court Road and pick up an import for 50 quid more.
I believe that you can also use them to play games ;-)