I just got a Raspberry Pi Model B (700 Mhz ARM chip, 512 MB RAM, 16GB SDHC card). You can find the site at
http://raspberrypi.org
This is a little ARM-based single-board computer that runs Raspbian (Debian) Linux and has Ethernet, 2 USB ports, and HDMI out (source:
http://raspberrypi.org). It uses SDHC for storage. It also can be powered from USB.
It was $35 for the board, but I got a case, SDHC card, powered USB 2.0 hub, wireless, USB-> Serial adapter, and a 5 port USB-powered Ethernet switch for it. All of this plugs into the USB hub, and is powered from one outlet.
It's meant for hobbyists. So far, I've done the following:
1. Run a serial cable to my Commodore 64 to use it as a serial terminal.
2. Run a wireless access point on it so I can use Wireshark to debug packets across the wire.
3. Run OpenSSHd for other project.
All of this equipment used to take a big desktop. Now it is a small stack next to my TV set/monitor.