The funding programs offered by the federal ministries support a variety of research areas and preferentially fund research networks. Calls for proposals as generally designed for a specific topic and a defined time span. The majority of research funding by the federal government is awarded through programs by the federal ministry for education and research (BMBF). But the other federal ministries also award grants for research projects.
The Förderkatalog des Bundes is a public database where you can find information on more than 110.000 current and completed projects (only in German).
The Research and Transfer Department provides information on current calls as well as support for your proposals.