The Tactile Design Kit
Once in a while we get a freebie so awesome due to its usefulness and the thought than went to it. Here’s one example.
The Tactile Design Kit is a physical, interactive web design kit created to facilitate client conversation and brainstorming during the discovery and design phase.
Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.