Tinker.it made a pretty neat little shield called the EthernetShield, so I figured I’d pick up a couple to make some projects.
The Ethernet Shield is designed to allow the Arduino base module to connect to the internet easily as a standalone unit. The module carries an onboard WIZnet W5100 Ethernet chip, which provides a network (IP) stack capable of both TCP and UDP, as well as a standard RJ45 Ethernet jack. It supports up to four simultaneous socket connections. An Ethernet library writes sketches that connect to the internet using the shield.
The Ethernet shield connects to an Arduino board using long wire-wrap headers which extend through the shield. This keeps the pin layout intact and allows another shield to be stacked on top.
Update: Using the Ethernet Shield with the Arduino Mega (Thanks to the folks at NKC for figuring this one out!)
Ethernet library: http://arduino.cc/en/Reference/Ethernet