ASUS makes this pretty cool looking sub-notebook PC called Eee PC. Even though this computer has been out for a while, I just recently learned of its existence. It seems like a good competitor to the OLPC.
It has a 900MHz Intel CPU, either 256MB, 512MB, or 1GB of DDR2 RAM, and either a 2GB, 4GB, or 8GB flash drive depending on the model. They all have a 7 inch screen with 800x480 resolution and built in 802.11g wireless. With no moving parts for the hard disk, this PC should be very quiet.
It comes installed with a customized version of Xandros Linux which can be updated from Debian repositories. It can also run Windows XP, which can be purchased for $40. The default install boots in (a very impressive by today's standards) 15 seconds.
WikiPedia has more information and here are some reviews that go into more details about the device:
I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve.
– Bilbo Baggins [J.R.R. Tolkien, "The Fellowship of the Ring"]