Scott Hanselman goes ga-ga for the SideShow API, the Vista functions for auxiliary displays. When I was first told about SideShow quite a while ago, the emphasis was on displays embedded in the outer shell of the notebook, just as clamshell phones often have a little aux display on their surface. I wrote an article back in 2004 in which I was more excited about "REM mode" applications (applications which can be run by a computer that's somewhere between hibernating and fully awake) than by the aux display itself.

Happily, the SideShow APIs seem to be fully decoupled from the physical attachment of the display, so Scott's excitement is primarily about using the SideShow APIs from one's main desktop machine to drive alternate displays.