I'm surprised I don't see mention of Waze here. It's a great new free Nav app for BB, iPhone, and Android. It provides turn-by-turn voice prompts as well. One of the really nice features which is only useful if a lot of people use Waze is real time traffic based on your speed. There are also features that allow users to easily post traffic info, speed traps, etc. Definitely worth a look -
www.waze.com
Regards,
SMF