EtherMega from Freetronics

The EtherMega is a 100% Arduino Mega 2560 compatible board that can talk to the world. Do Twitter updates automatically, serve web pages, connect to web services, display sensor data online, and control devices using a web browser. The Freetronics EtherMega uses the same ATmega2560 as the Arduino Mega 2560 so it has masses of RAM, flash memory, and I/O pins, and also includes the same Wiznet W5100 chip used by the official Arduino Ethernet Shield, so it’s 100% compatible with the Ethernet library and sketches. Any project you would previously have built with an Arduino Mega 2560 and an Ethernet shield stacked together, you can now do all in a single, integrated board.