You might be interested in bidding systems for enrolling in courses. The National University of Singapore has one http://www.nus.edu.sg/registrar/events/module-enrolment.html

"All students are given an equal amount of points per semester to bid for modules... The allocation of modules is based on the lowest successful bid points against the last available quota for the module at the end of each bidding round. If supply (module quota) exceeds demand (number of bidders) for a module for any bidding round, the lowest successful bid will be 1 bid point. If there is a tie in the lowest successful bid points, the outcome will be based on first-come-first-served. Unsuccessful bidders will be fully refunded. Any unused bid points after each round will be carried over to the next bidding round or to the next semester at the end of the registration exercise."