This demo has been in use for a long time now, but it's so good I thought I would share it...

Omniture SiteCatalyst Demo

Simplicity is the core message in this one and the value proposition is very easy to understand. It's a little long but comes with navigable chapters to jump around.

The animation uses gentle transitions, innovative pre-loaders, nice layering, and lots of white space. The background music can be a bit much but the volume can be controlled independently of the narration. The female narrator is excellent.