The Raspberry Pi is a single board computer that runs Linux (and a few other operating systems). I was origonally designed as a cheap solution (under $40.00) for teaching students about computers. Since then it has taken the DIY community by storm. Check this out for a complete history of the Raspberry Pi.
The Raspberry Pi is on a single credit card size board and comes with a lot of "stuff" packed into that small package. An ARM 700Mhz Broadcom CPU powers the system with 512M of RAM. On the Revision B board that I have, there are two USB interfaces, eithernet, HD Audio, Composite Video, and HDMI Video out. One of the great features for the hobbiest is the GPIO port that you to interface this board to what ever you can dream up.
This secion covers articles, notes, and gust ramblings of what I have learned about the Raspberry Pi. I hope others find it useful.
Raspberry Pi Website : Quick Start Guide : Raspberry Pi Forums | Raspberry Pi Wiki