New from the fine people who have brought us the Beagle Board, we now have a smaller, lighter, but powerful single board linux computer, Beagle Bone! We like this move to a more compact and integrated SBC. For example, there is onboard Ethernet and USB host, as well as a USB client interface (a FTDI chip for shell access). It even comes preloaded with Angstrom Linux on the 4 GB microSD card!
The Beagle Bone is a great step up from microcontrollers (such as AVR, PIC, ARM Cortex M3, 8051, Propeller, etc) to microcomputers. Unlike a microcontroller, where the FLASH, EEPROM, RAM, etc is all in one chip, a microcomputer has them separated out, like a classic computer such as a desktop or laptop machine. The Beagle Bone has a main processor core running at 700MHz, a chunk of 256M DDR RAM, and permanent storage onto a microSD card. This makes for a powerful machine, that has no problems running Linux, a webserver, Python, FTP clients, SSH, etc.
The Bone also has great accessories built in, such as onboard Ethernet with 10/100M connectivity, mini USB port with TTL serial converter, JTAG debugger for advanced hacking, USB A host port for connecting a hub/WiFi/etc, power management IC that keeps the board safe from a misplugged adapter, and tons of 0.1" spaced breakouts
One of the powerful abilities of the Bone is that it has I2C, SPI, and GPIO at a hobbyist-friendly 3.3V level (instead of the more difficult to interface 1.8V) while also running complex applications such as a webserver. This allows for more complex projects that would tax an Arduino.