Mod-Version of Google Apps (International Ready)
For a long time, I only used the Navigation and Map apps from Google. These are excellent apps of course and even though the International Voice Navigation has not been officially 'turned on' yet by Google, of course there is a mod-version and it is awesome (its the familiar turn by turn voice directions you've probably seen in cars for Europe and Asia). If your curious to try it (and I know you are) the mod-version is called "Brut Google Maps" and here is the download link.
Update Nov 14, 2011: I just started using the Cache feature in the Brut version. It is excellent even though its not as comprehensive as downloading a map in Locus noted beow.
Basically, Google Brut stores all the maps/zooms you view while online in a SD CARD Cache and then let's you use them offline. So for example, if I want to see my local day to day area offline, I first go online via WiFi at home, view the different local places, streets, etc and as I am doing so a copy is automatically stored. Then when I am offline, I can still see the map because its stored in the SD Card Cache.
Wait, Take It Offline with Locus!
Now, on a separate note, I always found it frustrating and expensive to use Google Nav/Maps via my mobile phone's data service (Edge, then 3G, then 4G, etc.). I mean it worked well enough but like everything else on mobile networks it tended to be a bit slow and you gotta be in range of a cell tower (otherwise you just see a GPS marker on a blank screen because no map-tiles can be downloaded to your phone).
Well, there is an alternative of course, just download the maps you need most. That is, you can store the maps offline and use your GPS to find where you are and where you want to go! Its much faster and its a growing trend these days as it is great for tourists and hikers.
Locus Free is an excellent app that let's you, among many other cool things, download maps to your phone. These can be pulled up and used along with GPS anytime.