Their increasing capabilities and declining cost make video projectors widespread and established presentation tools. Being able to generate images that are larger than the actual display device virtually anywhere is an interesting feature for many applications that cannot be provided by desktop screens. Several research groups discover this potential by applying projectors in unconventional ways to develop new and innovative information displays that go beyond simple screen presentations.Todays projectors are able to modulate the displayed images spatially and temporally. Synchronized camera feedback is analyzed to support a real-time image correction that enables projections on complex everyday surfaces that are not bound to projector-optimized canvases or dedicated screen configurations. In this talk I will give an overview over our projector-camera-based image correction techniques for geometric warping, radiometric compensation, reduction of global illumination (such as inter-reflections) or view-dependent effects (such as specular reflections), increasing focal depth, and embedding imperceptible codes with a single or with multiple projection units. Thereby, GPU-based real-time rendering and computer vision on graphics hardware are tightly coupled. Such techniques have proved to be useful tools for many real-world applications. Examples include ad-hoc stereoscopic VR/AR visualizations within everyday environments, quality improvements for (semi-)immersive VR projection displays, on-site architectural simulations, augmentations of museum artifacts, video installations in cultural heritage sites, projections onto stage settings during live performances, presentations using mobile (pocket) projectors, outdoor advertisement displays, digital illumination and projections in modern television studios, computer games, and more.