As part of a talk for Playful 09, I built a replica of Donal Michie's MENACE - Matchbox Educable Noughts And Crosses Engine.
MENACE is a machine made out of 304 matchboxes, which plays noughts and crosses - and, over time, actually learns to play it better.
More information, together with notes and slides from the Playful talk, can be found at shorttermmemoryloss.com/menace/, and there are more pictures at Flickr.
The talk and the machine were featured on BoingBoing, Gizmodo, MAKE Magazine and numerous other online sources. It also appeared in the print edition of Dutch newspaper NCR Next (cutting).