Mock-up tool

If you are and have a habit of producing very quick and rough mock-ups with a pen an a piece of paper (or maybe occasionally using an Table PC), then you might be interested in Balsamiq Mockups. This is an Adobe Air application that allows you to paste together quick mockups by dragging and dropping pre-defined templates onto a work area, such as a browser window, menu bar, image holder, etc.

It’s a really simple idea and works really well

Source: Interface Matters