Back to RPi Expansion Boards.
The Gertboard is one of the expansion boards, sold for some time in a kit form. It was nicknamed after Gert van Loo, its developer and one of the principal Hardware Engineers for Raspberry Pi, and was announced on 17th December 2011: 
Gertboard Availability Announcement includes links to assembly and user manuals.
As of 2013-01-22, it is now possible to order pre-assembled Gertboard through Element 14: http://www.element14.com/community/docs/DOC-51726?ICID=raspberrypi-gert-banner User manual is available at : http://www.element14.com/community/docs/DOC-51727/l/assembled-gertboard-user-manual?ICID=gertboard-techdoc
Additional Details can be found on the Raspberry Pi Forum here.
Gertboard test suite has been released in Python. These are written to be functionally identical to the original C programs, but have been rewritten from scratch. There are versions for WiringPi for Python and RPi.GPIO.