Is there an app that will vocalize (text to speech) a message (SMS)? When I'm driving with a headset active (Bluetooth or wired), I want my Android to read me any incoming text messages.

Any references?
There are a number of apps that will do this.  DriveSafe.ly is what I use right now, but haven't really had the opportunity to thoroughly test their TTS engine.  It can also be set up to start whenever bluetooth is paired, or if you put it in a car dock.

I did try another one out a few months ago, but can't remember the name right now.  A search through the app market (or your favourite online app site) may reveal some more.