It's quite inevitable, really: After Google announced free turn-by-turn GPS navigation for Android devices -- followed by Nokia's decision to offer the same on its smartphones -- the price of full-featured GPS navigation apps on other platforms is hurtling toward zero.
Case in point: MapQuest 4 Mobile, a free GPS navigation app for the iPhone, now offers "basic voice guidance."
The app will tell you when you need to take a turn and, if you get lost, it will warn you that you're off route. Other features include the option to save maps and routes on MapQuest.com to retrieve on your iPhone, easy POI finding via the OS X dashboard-like Place Carousel, the ability to find you on a map or in relation to a route and free form search.
The app is available for free in Apple's App Store.