Why do people donate their time and creative thought process to Wikipedia? Or the open source movement? When you stop and think about it you realize that there are many activities that people engage in, even over a long period of time, that require high expertise, and yet are of no monetary or even career building benefit. People like to feel that they are making progress. They like to feel that they are learning and mastering new knowledge and skills.

Small signs of progress can have a large effect — Because mastery is such a powerful motivator, even small signs of progress can have a large effect in motivating people move forward to the next step in a task. At Linked In, they encourage you to finish filling in information on your profile by showing you how much information you have already answered.

LiveMocha is a website where you can learn languages. They have several forms of mastery and progress built in:

At a glance you can see where you are in the course, where you are in the lesson, and how much progress you have made overall.

They have points that you can earn by completing your training, as well as by helping other people learn a language you already know. The points can be accumulated and redeemed for access to premium learning exercises.