I am a strong proponent of using Genius Hour in the classroom. The program began with Google employees. They were free to spend one hour a week pursuing their own projects. This freedom not only led to great developments, like Gmail, but it also increased productivity in their traditional projects. I have found the same to be true in my class. The research and presentation skills that students hone during Genius Hour have consistently helped them in our other lessons.
The structure for Genius Hour in my classroom is simple. Students are free to explore any topic or idea that they are interested in. Yet it cannot be something they are already very knowledgable about. At the end of a set time, they must have produce something that can teach what they learned with their peers. In the past, I have had students create robotics demonstration, flute solos, crystal gardens, and even a functioning online store. The one common thread has been that we all learned a lot, and that I have been impressed with every project.