Video projectors have evolved tremendously in the last decade. Reduced costs and increasing capabilities (e.g. spatial resolution, brightness, dynamic range, throw-ratio) have led to widespread applications in entertainment, art, visualization and in other areas. In this chapter we summarize fundamental visualization and interaction techniques for projector-camera systems that are being used to display interactive content on everyday surfaces - without the need for optimized canvases. Coded projections and camera feedback allows measurement of the projected light on these complex surfaces and compensates the modulation, while also enabling computer vision based interaction techniques.