We present Silicone iLluminated Active Peripherals (SLAP), a system of tangible, translucent widgets for use on multitouch tabletops. SLAP Widgets are cast from silicone or made of acrylic, and include sliders, knobs, keyboards, and buttons. They add tactile feedback to multi-touch tables, improving input accuracy. Using rear projection, SLAP Widgets can be relabeled dynamically, providing inexpensive, battery-free, and untethered augmentations. Furthermore, SLAP combines the flexibility of virtual objects with physical affordances. We evaluate how SLAP Widgets influence the user experience on tabletops compared to virtual controls. Empirical studies show that SLAP Widgets are easy to use and outperform virtual controls significantly in terms of accuracy and overall interaction time. Author Keywords Tangible user interfaces, transparent widgets, augmented virtuality, dynamic relabeling, tabletop interaction, multi-touch, toolkit ACM Classification Keywords H.5.2 Information Interfaces...