Visual Cryptography
Slides wit principles
http://www.slideshare.net/valicac/visual-cryptography
Java applet for generating k out of n shares (very nice):
http://www-sec.uni-regensburg.de/vc/
links to VC software:
http://users.telenet.be/d.rijmenants/en/visualcrypto.htm
Java App for simple 2 shares VC:
http://www.r-hansen.com/tech/oti.html