If you’re lucky enough to be heading off to the States any time soon, this little beauty might come in handy. CoPilot Live USA is a GPS navigation app that stores its maps on your phone. As such, you don’t have to be online to use it, so you won't incur outrageous data costs. Bonus.
CoPilot Live USA has 3D maps, Lane Assist arrows, millions of points of interest and a trip planner.
Compatible with Android 1.5 and up.
(Thanks to swampy_donkey at HUKD)