Okay, it's a startup company, a no-name processor, and way over priced so it will probably disappear in this form very quickly, but it's a nifty new toy and a promising step.
www.oqo.com
In short, size of a PDA, 1Ghz processor, 20GB hard drive, 256MB RAM, and it runs a standard OS (ships with Windows XP, I don't know if it supports anything else). Not Windows CE or whatever they might be calling the stripped down PDA OS these days. The fully functional version of XP Home or Pro. WiFi, firewire, USB. This thing is pretty loaded.