The Raspberry Pi has a Broadcom BCM2835 system on a chip (SoC), which includes an ARM1176JZF-S 700 MHz processor, VideoCore IV GPU and 256MB RAM. It uses an SD card for booting and long-term storage. Raspberry Pi runs on Linux & possibly Android (someone is working on the porting). There is a Debian-based OS known as Raspbian which is optimized for this board.
You can get this board from Element14 for RM125.