I did a Special Concentration in Organizational Behavior! It is quite a challenge but overall very fulfilling, should you choose to go this route.

The process is quite extensive. You need to:

1. Choose your course of study, and demonstrate clearly why it cannot be done in a concentration traditionally offered by the university.
2. Create your curriculum, choosing courses across departments
3. Find an advisor who is willing to work very closely with you
4. Petition the Committee for Special Concentrations.
   (Generally, special concentrations that fall within a globally accepted field of study are the most viable. For instance, though Public Health is not offered by Harvard College, it is a globally recognized field and therefore legitimate as an SC).

In my year, only 3 students (I believe) graduated with a Special Concentration. Very exciting!