If you want it to work like a garmin, tom-tom, or magellan, download:
Co-Pilot
Sygic
I use Android Sygic. The maps (Tom-Tom I think) are frequently updated at no cost. The maps for US cost about $20 one time. Works great on my 8" screen. You can get maps for each continent if you are a traveler.
No broadband connection required while using the apps. Update when connected to WIFI.
My $650 Garmin from 2005 cannot be updated since 2008. It still works, but POI and features are dated.