Book of Vista
For the past six months whenever I want to know something about Vista, I've consulted a thick book we used to call "The Book of Longhorn". It's a nice summary of all the important features, written by people in the product groups responsible. I'm pleased to say that it's now available on line and you can download your own copy. No it doesn't have every single detail, but it does have enough highlights to give you the basic idea, which can be very helpful if you're trying to navigate among the zillions of cool features in Vista.
The speech section was written by Jen Anderson, Jonathan Garcia, Oliver Scholz, and several others in both our speech engine components and the user experience teams.