GUI MockUp Tools

We often need a tool to quickly mockup user interfaces to help Stakeholders/Client envision the screen interactions, data structures, and/or overall look-and-feel of a proposed system that we are helping define requirements for.

Popular GUI Mockup Tools

DesignerVista - http://www.designervista.com/

Firefox Pencil Addon - https://addons.mozilla.org/en-US/firefox/addon/8487

Mockup Screens - http://mockupscreens.com/index.php?page=Free-Download