MSDN magazine has this cool feature where , the images , if too big are shown compacted by default. However, when you click on the image for larger view, the image is shown larger in place rather than in a seperate popup. I was thinking, this is probably a useful feature to have if it is simple to do.

Example here ( third image has this behavior ):
http://msdn.microsoft.com/msdnmag/issues/07/10/NoiseDetection/default.aspx