Opazity is a new PowerPoint add-in that provides presenters and presentation designers the ability to create ‘opaque glass shapes’ without leaving PowerPoint. This effect can help hold and maintain a presentation audience’s attention by obscuring and hinting at something to be revealed.
Once Opazity is added to PowerPoint, the presenter first develops the slide and then, where the opaque glass effect is required, overlays the area with a standard or hand-drawn PowerPoint shape. With a few clicks that shape is converted into a transparent but blurred image of whatever is underneath. The presenter then applies a PowerPoint animation to the shape to reveal the image.
Opazity is compatible with PowerPoint 2007 and some earlier versions.
Read more info at the Opazity site.

