The base module is somewhat daunting with 40 pins. The module I built is the sockets and discrete electronics to breakout only the eight (8) lines necessary for the SPI interface.
I designed this module in development of a project using GHI Electronic's Panda II. GHI includes drivers for this WIZnet part. Note GHI's Rhino accepts WIZnet's module directly.
From left to right the pins are GND, SCLK, MISO, MOSI, CS, RESET, INT, and 3V3.
The primary advantages of using the WIZnet part is less code and RAM size necessary to maintain an ethernet stack, its low cost, and being accessible via methods that a microprocessor can easily handle.