Air Dictate is a clever little app that ports the power of Siri over to the Mac. Kind of. It doesn't have any of the bells and whistles of Siri (don't go starting conversations!) but rather, uses the extremely accurate speech recognition engine in Siri to dictate text to your Mac.
Basically, you talk into your iPhone 4S and words pop up on the Mac. You have to download a companion app on your Mac and make sure both the iPhone and Mac are on the same Wi-Fi network. After that, speak away and you'll see your Mac log down every word you say. Definitely worth the buck if you prefer talking to typing. [iTunes via CNET]