Google Maps. New off-line features
How to use Google Maps offline A nice, new, easy way to use if offline.
Forum Discussion
The AT&T navigator app (rebranded Telenav) allows for offline downloads. They are a couple gig (1621MB for central US), and are available for the west, central, and eastern parts of the US. I've been using it since 2010, and it has worked pretty well.
