I offer a ton of extra credit, and sometimes it is completely impromptu. Topics will come up, such as "Does looking at the sun really help you sneeze?" or "What is the exact meaning of i.e.?" or "Why do we sleepwalk." The environment I create is one that bonds students right away; make them feel like they are a true part of the school. Being a real person to them, while remaining their professor, allows for a higher level of trust between class members. Once I asked them to simply go and research something that they always wanted to learn more about and write a little summary. They loved it! They all had to use the internet/library, so it worked out well. Having them choose is a powerful tool - it really lets them become part of the material, and the class. I have never had any negative feedback, the students tend to try harder when it's a "want to" situation, rather than a "have to" situation, and a ton of psychologist back me up on that! :)