http://en.wikipedia.org/wiki/Sport_stacking

Sport stacking (formerly known as cup stacking) is an individual and team activity played using plastic cups. It originated in the early 1980's in southern California and received national attention in 1990 on The Tonight Show with Johnny Carson.

Participants of sport stacking stack and unstack cups in pre-determined sequences, competing against the clock or another player. Sequences are usually pyramids of three, six or ten upside-down cups. Proponents of the sport say participants learn teamwork, cooperation, ambidexterity, and hand-eye coordination.

Tournaments are governed by the World Sport Stacking Association. In 2004, the Association changed the activity's name from cup stacking to sport stacking to give it "immediate identification as a competitive sport."

Sport Stacking can be done with specially designed cups only (called Speed Stacks), because otherwise the cups would stick together. Made of durable plastic, they have holes in the bottom to allow air to pass through quickly when stacking the cups together and are designed so they can be quickly separated from each other when stacked.