NEWS:In December 2008 I ported this design to the Terasic DE1/Altera Cyclone II Starter Kit (it is the same board, so you can get whichever is cheaper where you live.) These have a similar capacity FPGA (EP2C20), and a fairly similar feature set, just lacking the Ethernet connector. However, these boards are much cheaper, with a list price $150 instead of $1200, and a discount ($120) for students. The last two pictures show the DE1 board. There is now also a DE0 board which is even cheaper, at $120/$80.
One of the pictures also show the Olimex ENC28J60 Ethernet module, which happens to match the pinout of the DEx GPIO connectors with only a connector replacement.
The source code to these various projects are at:
Download a zipfile with all the images (26.4 MiB/27.7 MB)