My husband works for a big company, and the human resources department comes up with all kinds of ways to motivate the employees. These are all centered around either safety or production, and they have worked very well.
If the workers in his sector go without having an accident on the job for sixty days, they get a pizza party. If they go ninety days, they get to eat steak, while the other sectors have to eat hot dogs instead. This little bit of negative reinforcement spurs the losers on toward safer practices.
To keep employees happy, the department of human resources also gives out what they call incentive checks every four months. The amount is a percentage of how much they earned during that time period, and the harder you work, the more you can earn.