W5100 Ethernet Shield for Arduino
The Ethernet Shield has a standard RJ-45 connection, with an integrated line transformer and Power over Ethernet enabled.
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, Crowduino and Mega (using the Ethernet library). The onboard microSD card reader is accessible through the SD Library. When working with this library, SS is on Pin 4.
There is also the w5200 Ethernet Shield for you.