Cow tipping is a rural activity in which people sneak up on a sleeping, standing cow in the dead of night and push it over sideways. It is considered an urban legend since cows do not sleep standing up and are very heavy. Cow tipping is supposedly a form of entertainment primarily undertaken by drunk, bored adolescents. Although in recent years, it's been suggested that cow tipping is an urban myth.
Tips on maximizing fun during a cow tipping session.
Cow Tipping at UC-Davis
Description of cow tipping and student discussion on the subject.
Cow Tipping on h2g2
Describes rise in popularity of cow tipping and the sports legality.
The Statics of Cow Tipping
A look into the physics of trying to tip a cow.
The Straight Dope: Is There Really Such a Thing as Cow Tipping?
Several viewpoints critique the idea of cow tipping.
The Time-Honored Urban Activity of Cow Tipping
Looks at whether cow tipping is truth or fiction.
Wikipedia: Cow Tipping
Examines the evidence that cow tipping is an urban myth.