Dragon naturally speaking is still available at nuance.com (or something like that).

I had an earlier version (my first foray into speech recognition) and it worked pretty well. The more time you spent training it the better it got.

It's more pricey than the voice recognition I'm using specifically for games, but dragon has a whole load more feaures.

Supposedly windows vista has got pretty good speech recognition built in - and I think someone on this forum was talking about interfacing with that for us multiboxers.