Combo of the Gertboard, Arduino and AT mega, According to Element 14 the price is <£18.87*
Pi site info : http://www.raspberrypi.org/archives/5308
Element 14 more detailed description : http://www.element14.com/community/docs/DOC-64326
Price is quoted from the website.
Looks interesting.
http://www.nikeairmaxfreedom.com air max