I use Nav Free USA,. It downloads the maps you need, then allows to you to use them whenever you want, regardless of whether or not you are on the inter webs. It's free too.
Droid OG (Retired), Droid 2 (Retired), Droid 3(Retired), Droid X (Retired), Droid X2 (Retired)
Samsung Galaxy Nexus (Unlocked, Rooted, Overclocked, Undervoltaged), Samsung Galaxy Tab 10.1 (Stock)
Nexus 7 (Unlocked, Rooted, Undervoltaged)
Please click "Thumbs up" if somebody posts something helpf