Google just announced a FREE beta version of a turn-by-turn mobile GPS navigation app, with voice and text input. Right now, it's just for Android OS 2.0; iPhoners will have to wait. (Incidentally, this is another reason that, contrary to my earlier post, Android phones will gain momentum, ugly though they may be.)
Attention Garmin, Tom-Tom, and AT&T Nav: "My name is Google Montoya. Prepare to die."