Want your Arduino to check email? How about sending a twitter (which can then be easily forwarded to a phone via SMS)? Or grabbing data from a website? There are so many possibilites for projects that connect to the Internet to get data, now there’s an easy way to do it with an Arduino.
This shield allows you to add and use an XPort or XPort direct(+) Ethernet module (they cost only US$30-$50) using any 4 pins. All of the TCP/IP stack awfulness is done for you in the module so its super easy to just connect to any server.
Arduino Ethernet (XPort) shield kit: [Link]