In terms of the number of available scholarships for full-time PhD study at Freie Universität Berlin, the FUB-CSC Program is certainly your best option.
Some of the structured doctoral programs and research training groups of Freie Universität Berlin have their own scholarship programs. These scholarships are given away on a competitive basis. Calls for applications are open to Germans as well as international applicants. Calls are published yearly, in the case of some programs only every 2 to 3 years. For information about these scholarship opportunities, see the homepages of the individual programs. A suitable starting point is the List of Graduate Schools and Research Training Groups at Freie Universität Berlin.