"GPS maps to travel in the USA."
As you may well have been able to work out just from the name of this application, Roadnav is a navigation system for all types of vehicles that you can download for free, and runs on practically all platforms. It lets you orientate the roads in any place of the USA, via "homemade" but effective resources.
Roadnav can get the exact actual position of a car via a GPS device, draw street maps of this area, and offers verbal explanations to get to any point. This way, if you have a GPS in your car and a laptop, you can use Roadnav to get to your destination or to avoid getting lost in a place you don't know.
The Roadnav program can also work without being connected to the Internet! At the moment Roadnav only has maps of the USA, and takes data to elaborate the maps and routes from specialized US centres.