If you are looking for low cost and home made Ethernet shield, you can try this project. Boris Landoni has made low-cost Ethernet shield for Arduino using traditional mounting components. This feature makes the circuit accessible to those who haven’t the equipment to assemble SMD components. The data-rate is limited to 10 Mbps.
The shield is based on a Microchip ENC28J60 chip that interfaces with Arduino and data conversion according to the Ethernet protocol. It integrates the MAC controller, an 8 KB Transmit / Receive Packet Dual Port Buffer and a circular FIFO managed at the hardware level, allows the programming of data retransmission in case of collision.
DIY Ethernet shield
Project Firmware, Schematic and Documentation