As I think more about the issue of motivating without money, I keep coming back to one of my favorite business books - Soul of a New Machine by Tracy Kidder. Kidder won the Pulitzer Prize for this fantastic book, in which he traces the efforts of Tom West and his product development team at Data General as they develop a new computer in the early 1980s. West employs a variety of unorthodox management methods to drive his team to high performance. Many of my students describe him as manipulative. Whether they approve of his methods or not, however, all students learn from this story that West has created an exceptionally high level of intrinsic motivation among his staff.
One particular lesson that we learn from the book is that many employees are motivated to work very hard on a particular exciting project if they believe that other "cool" projects will be available to them if they perform well in their current work. In Soul of a New Machine, they call this the "pinball theory of management" - i.e. if you excel on this project, you get to work on another exciting one. In short, many people want the promise of interesting future work that will help them grow and develop, and that will challenge them in a unique way. They do not necessarily need to be motivated by a huge bonus at the end of the project (thogh they would like that too!). They might also be highly motivated by the next opportunity that will come available to them.