Whats the best way to create interactive application prototypes?

Question

The question should be interpreted from a general point of view and not targeted solely at web apps or desktop apps.

I have been looking around to find a simple and

Answer 1

Quick and dirty paper prototyping: PowerPoint (see: Powepoint Prototyping Toolkit)

-Great for easily putting together prototypes that can be presented. The slide nature can also serve as a substitute for mock interaction. Downside is lack of standardization. Not for disciplined projects.

Disciplined paper prototyping: Visio

-Standardized and full featured, but more cumbersome

Interactive prototyping: Visual Studio

-Very quick interaction building using drag-n-drop and events. Can be data driven. You can even build a prototype 'base' as a starter kit. Only downside is the temptation to actually make it THE production application. ;)