Ronnie Hinton of Florida made a tunable six-string cigar box guitar, base on the project in MAKE vol. 4. As the video on his site shows, he can play a decent tune or two on it!
From the pages of MAKE:
Cigar Box Guitar by Ed Vogel in MAKE volume 4 - preview online (digital subscribers can read entire article)
http://blog.makezine.com/archive/2008/07/sophisticated_cigar_box_g.html