OsmAnd is a great free offline navigation app. If you're in an area with adequate OpenStreetMap coverage the offline capabilities of OsmAnd blow Google Maps away.
An old OsmAnd problem was that its map rendering was very slow. An app update and new map format speeds things up a lot. It's more accurate too, so coastal areas are no longer rendered underwater. Offline routing is improved as well, and the user interface looks a bit cleaner.
The old OsmAnd maps don't work in the new OsmAnd app, so you have to redownload 'em all.
The bad news: you can download maps from the OsmAnd download screen, but there's a limit of
The good news: there are ways to bypass the download limit. And there's a good reason for bypassing the limit. The maps from OpenStreetMap are made by people like you and me for free. Selling the hard work of all those volunteers is plain wrong.
You can download maps without limits from
To download as many maps as you like from within OsmAnd you have to reset the counter. One way is to enter the app manager and clear the OsmAnd settings. You'll have to reconfigure all your settings, but the download counter is reset to zero by a data wipe.
Tip: Configure OsmAnd, then make a Titanium backup before you download any maps. When you hit the download limit you just restore the Titanium backup to start with a clean slate without losing your settings. It doesn't have to be a Titanium backup, any app that can backup apps with their settings will do the job.
Update: Don't want to bounce back and forth between Titanium and OsmAnd to grab some new maps? As aelmahmoudy kindly pointed out in the comments below, you can also download the maps and voices from http://download.osmand.net/list.php?d=-1. Maybe one day someone will make an Android app that does the downloading for you (scheduled please!) and puts 'em the right folder all by itself.
Google Maps lets you cache small maps offline, but you need an internet connection to calculate routes to navigate. Route 66 wants money for voice navigation, but first time users get a free one month trial. Install Route 66 just before your vacation so you can use your free month to the max. Route 66 reads your SIM card details to see if you qualify for a free month of voice navigation, so if you pop a disposable prepaid SIM into your phone...
NavFree pulls its maps from OpenStreetMap just like OsmAnd does, but the files are a lot smaller. You can save almost half the space if you use NavFree, which can be useful if you want to store a lot of maps for many states and countries. Unfortunately NavFree has ads (OsmAnd doesn't) and it requires an internet connection to search for addresses. OsmAnd can search offline (which explains the bigger map files).
• OsmAnd (Google Play Store)
• Google Maps
• NavFree (Google Play Store)