A $25 version is planned, but only the $35 model is available for preorder currently. It includes a Broadcom-built ARM CPU/GPU, 256MB of RAM, and ports aplenty with an SD card slot, HDMI, RCA video and audio out, MicroUSB (for power), two USB 2.0 sockets and an Ethernet connection. (The $25 model will exclude the Ethernet and USB ports.) Wi-Fi is supported via a USB dongle.
The Raspberry Pi foundation has licensed Premier Farnell and RS Components, two British companies, to sell the pint-sized PCs. Hit those links to buy some Pi of your own, but be forewarned: they're getting hit pretty hard right now and are dropping out intermittently.