For the Netzer Playground some extension boards were developed:
The Netzer Playground enables quick development of circuits around the ethernet gateway Netzer from MoBaCon. Netzer is simply put into the prepared socket.
For new Eagle projects Netzer in a library that is easy to use (Release of 2012-05-22):
Open (Eagle version 5.X)
Also included are footprints and schematic device for the extension port to develop own extension boards for the Playground.