Thumb Wrestling « Hand Games

Monochrom's Massive Multiplayer Thumb-Wrestling - Explains the basics as well as multi-player variations. Includes photographs.
Samurai Thumbs - Describes how to play this game using helmeted thumb wrestlers as warriors. Includes some variations.
Thumb Wrestling - Describes how to thumb wrestle, with a snake in the grass variation.
Wikipedia - Thumb Wrestling - Description of how the game is played.