The Sony Vaio PCG-U101 is a very tiny yet full-featured subnotebook. Sony only sells it in Japan, but several importers make it available in the US as well. I've got one, and I run Linux on it. This web site will give full details on installing and configuring the system, but the summary is: almost everything works perfectly, including the wireless network card.
The only significant lack is support for the special keys via sonypi, and I hope to resolve that soon. It'd also be nice to be able to tap the pointing device to click, but that's non-fatal — and should also be resolvable.
There's more images on the pictures page, and much more system detail on the Hardware Chart.
August 6, 2008: So, I'm running Fedora 8 on my U101 these days, and will update to 10 when it comes out. I'm keeping an eye on the current crop of "netbooks", which is the new name for laptops in approximately this form factor, but really, nothing is as good as this little computer from five years ago. The HP 2133 Mini-Note may come close, but has some disappointing deficiencies. I'm looking at getting a PATA SSD to extend the life of my U101 for another couple of years. (This one is rumored to be $45 for the 8GB model, but would need an adapter of some sort, and I'm not sure how that'd all fit.) I'll make a few updates to this site as I work on that.
November 19, 2003: Whew, what a slacker I am. I've got lots more stuff to add here, coming Eventually. Particularly, I've updated to running Fedora Core 1 instead of Red Hat Linux 9. But other little bits as well.
July 24, 2003: This update section was getting a little long, so I've decided to clear it out. This wasn't really meant to be a weblog. I've put up a section Dynamism to summarize my purchase experience — I think that was the most important info that was here. And lots of other info from people's e-mail and my experimenting will go up RSN.