BE-300 is a palm-size computer that was sold by Casio a few years ago. It is now discontinued but it can still be picked up on ebay at a very low price.
The highlight for me personally is that it can be used as a digital library for a very low price (around $40, used, nov 2005).
You can look at hw specs here: http://www.casio.com be-300 site
The battery lasts about 4-5 hours (when reading) and takes 3-4 hours to charge fully.
The unit takes only a second or two to come out of standby mode. I was a little worried about this point, given that Windows is typically bulky and slow, but the one in BE is light as a feather. I can use it to read anywhere - waiting in a line, on a bus, waiting for a train in subway station..
The screen is not very readable under bright light. Under direct sunlight you can't see anything at all. However, if you go outside and sit in a shade, it's quite possible to read. Environment like a subway car is a bit of a problem because you have bright light overhead which creates reflections, but at top brightness it's not too bad, and I'm thinking right now of fitting a transparent but slightly rough-textured piece of film on top of screen that would eliminate reflections in such environment.
Don't get me wrong though: I've read a few books in subway already and hadn't had much trouble with reflections. It could be a bit better but it ain't bad.
I'll update this page if that goes well enough.