Work in progress - see http://forum.jeelabs.net/node/457
Derived from code by Guido Socher and Pascal Stang, hence under GPL2 license.
The home page for this library is http://jeelabs.org/ethercard
You can download this project in either zip or tar formats.
Unpack the archive and rename the result to EtherCard.
Put it in the libraries folder in your Arduino sketches area.
Restart the Arduino IDE to make sure it sees the new files.