raspINGA is a INGA compatible radio transceiver for the RaspberryPi. INGA was developed at IBR as Inexpensive Node for General Applications and became part of many projects. raspINGA can be used for a cheap and easy communication between Wireless Sensor Networks and embedded PCs - like RaspberryPi or even a BeagleBone - based on IEEE 802.15.4 standard.
All relevant files (schematics) can be checked out of the SVN:
http://svn.ibr.cs.tu-bs.de/project-cm-2012-inga/public/hardware/RaspINGA
If you want to try wiggling a test PCB out of us, contact Felix.
A Raspberry kernel with the neccessary patches can be found in out GIT: PI Kernel with raspINGA support. You probably also want the lowpan-tools for Linux.