You can use the Arduino Ethernet Shield to connect your Arduino to the internet in mere minutes. The shield is based on the Wiznet W5100 Ethernet Chip. This is the latest R3 version (2013) of Arduino Ethernet shield and The improvement includes the addition of the Arduino standardised 1.0 pinout and a Power over Ethernet (PoE) Upgrade option.
There is an onboard micro-SD card slot, which can be used to store files for serving over the network. It is compatible with the Arduino Uno and Mega (using the Ethernet library). The onboard microSD card reader is accessible through the SD Library.
- Operating voltage 5V (supplied from the Arduino Board)
- Ethernet Controller: W5100 with internal 16K buffer
- Connection speed: 10/100Mb
- Connection with Arduino on SPI port
 W5100 Datasheet
 Bildr Tutorial (Server)
 Bildr Tutorial (Client)