In writing my review of the iPhone 4S I got to spend some time playing with the Siri voice-recognition engine. And so I made a video, so you could see it in person. It's embedded in the review itself, but I've also added it below as well as putting it in our (soon to be revived) Macworld Video podcast stream.
(Eagle-eyed readers will note a particularly unfortunate—albeit funny!—transcription error when the iPhone 4S tries to spell its own name. It was left in place in the interests of verisimilitude. Such is life in our science-fictional universe.)