Nielsen Norman GroupEvidence-Based User Experience Research, Training, and Consulting
With a paper prototype, you can user test early design ideas at an extremely low cost. Doing so lets you fix usability problems before you waste money implementing something that doesn't work.
By turning all text into gibberish, a usability test can focus on whether the *layout* of a Web template helps users navigate and use the page.
Paper prototyping, card sorting, and traditional usability testing were all employed to guide the design of the 1995 Sun Microsystems' Web site.
Using Discount Usability Engineering to Penetrate the Intimidation Barrier,' paper by Jakob Nielsen on simpler and cheaper ways to a better UI;with examples of fast usability projects.