3DTin is a free web-based program for creating three dimensional models. 3DTin provides templates that you can use to develop models or you can build a model completely from scratch. The service is completely free to use as long as you allow your models to be labeled with a Creative Commons license and put in the 3DTin gallery. The gallery is a great place is to find examples of what can be created in 3DTin. Models that you create can be exported for use in other modeling software.