http://www.raspberrypi.org/ Stick-of-gum computer with an ARM chip, pretty good video hardware, USB 2, and 256MB of RAM.
And that's it. You'll have to add a USB hub, a keyboard, mass storage, a mouse, and a video display/TV.
Intended price point: $25. (And, obviously, when you add the necessities, it'll really cost $100 or more.)
I'll probably donate some units, when it becomes real enough.
Incidentally, I dropped out of the OLPC "software charity" effort a while ago. I just wasn't any use to them, since I have zero temperament for porting Linux, so I donated my hardware and some more cash to the local SF group, so that they can deploy in, I think, Haiti.
In addition, as interesting as a near-indestructible, very low power, very low cost computer was, I simply could not type on the OLPC keyboard. Makes it tougher for grownups to steal the computers, I guess.
Good news is that, partially due to OLPC, open source unix has gotten a lot better at low power computing, so doing OLPC-like computers is dramatically easier now than it was then. Hopefully, a bunch of undergrads can port Sugar to it in a few weekends.