PROTOTYPING RESOURCES
The following is an unpaid (and hopefully unbiased) list of vendors that can help you create high-fidelity prototypes.
TOUCHSCREEN RESOURCES
GestureTek (http://www.gesturetek.com) has a wide range of products, from surfaces to displays.
Mass Multimedia, Inc. (http://www.touchscreens.com) is a source for touchscreens, touchscreen overlays, and software.
NextWindow (http://www.nextwindow.com) sells large-scale touchscreens and touchscreen overlays for displays up to 120 inches.
Synaptics (http://www.synaptics.com) has a developer toolkit and software for its OneTouch touchscreens.
Cubit (http://nortd.com/cubit/) is an open source project and accompanying kit for creating a large, Microsoft Surface-like multitouch table.
PHYSICAL COMPUTING RESOURCES
Toradex (http://www.toradex.com) sells motors and USB sensors that are useful in prototyping physical environments.
SparkFun Electronics (http://www.sparkfun.com) sells all kinds of sensors, tools, and components for DIY prototypes.
Infusion Systems (http://infusionsystems.com/catalog/) has lots of environmental and human sensors as well as software as part of its I-CubeX product line for making prototypes.
MakingThings (http://www.makingthings.com/) has a full line of tools, sensors, motors, and software around its Make Controller. Good for beginners.
AlphaPrototypes (http://www.alphaprototypes.com/) will make plastic prototypes from 3D CAD drawings.
d.Tools (http://hci.stanford.edu/dtools/)is a hardware and software system for ...