Iphone GPS?

Can my iphone be used as a navman?? As in a GPS with voice commands?? Is there an application i can install to allow this??

Related posts:

1. Twitter With Your iPhone
2. What is the best iphone GPS application?
3. does the gps on iphone need internet connection?
4. Should i buy an Iphone 3g or a TomTom Gps?
5. What is the application on the iPhone where u can track gps on 5 numbers?