There's no shortage of iPhone navigation apps out there, but we can't say we've seen too many that come with 1.6GB of offline map data -- especially for free. That's the hook for NavFree USA, which just went live in the App Store -- sure, it also has some interesting social features like crowdsourced map updates and navigating to friends, and you can buy add-ons like traffic and speed camera info, but we think most people will use the free turn-by-turn and call it a day. That is, until Apple builds navigation directly into the OS. PR aft