If you have a Nokia Symbian device, then you can get Ovi Maps installed on it.
Ovi Maps allows you to download map files for as many countries as you want and store in on your memory card.
Once that's done, you can set Ovi Maps to offline mode and still be able to use it to get directions.
If you get a local SIM, then it will be able to show you rough location data too.
I find Google Maps' public transit planning feature very handy too
but I often cannot use it on roaming.
Instead, I use this app called Métro (available for iPhone, BlackBerry, Symbian, Windows Mobile, PalmOS - no Android or Windows Phone 7 version yet) that allows you to store public transit information data offline for many major cities around the world.
The full list of supported cities supported by Métro is available here ; you can also use the same page to customise your download in case you do not want the full package.
They are fairly regular with keeping their database up-to-date too.
EDIT :
Google Maps has recently launched a beta feature (only on Android phones though)
that allows you to save map data for a specific radius on your phone for offline usage.
Not as useful as downloading maps for a whole country like Ovi Maps allows, but if you have wifi access every now and then on the road then you should be able to take bits of Google Maps offline on the go.
EDIT 2
: Android users can also try out the free MapDroyd app that allows you download offline maps country-by-country.
The maps themselves are mostly barebones with no point-of-interest data.
travel.stackexchange.com/users/108/Ankur Banerjee
There are different handheld GPS units.
My favourite is the Garmin eTrex.
Garmin's own MapSource maps are usually quite expensive and require annual updates.
OpenStreetMap is a nice alternative; you should check the site if the coverage in the required area fits your needs.
The quality of data is quite okay too.
The map data can be stored offline in a Garmin handheld GPS unit , thus negating the need to have a mobile phone or a global roaming plan.
I am still amazed that all of Europe's maps fits on a small Micro SD card as big a my small toe nail.
travel.stackexchange.com/users/None/
FIrstly, even if you COULD get offline Google Maps, it's not that useful in non western countries.
Murmansk - the largest city in the arctic circle, is shown as just two streets in Google Maps.
Most of their coverage of Central Asia is next to useless as well.
In addition, you need some serious storage for offline google maps.
What I eventually settled with was NavDroyd - for Android, but there'll be equivalents for iPhone etc.
It cost a few dollars, but not much - and the maps are all totally free, as they just download the free Open Street Maps maps, which are vector graphics anyway.
It was fantastic.
The interface was a little clunky to me and took a few minutes to get used to, but once I had it sorted it was brilliant - even in Siberia, Kyrgystan and Mongolia! And being back in London
it's pretty fantastic here too, although I find it easier to use Google Maps here as it inclues other information I look for (Latitude).
travel.stackexchange.com/users/101/Mark Mayo
I've got a smartphone which can cache maps locally (it's a Nokia N900, but lots of other ones do that too, with a few notable exceptions).
Before I go somewhere, on Wi-Fi
I browse around the area I'll be visiting, so the phone downloads all the maps.
When I'm there, I can then navigate around without needing to download anything, just using the cached maps and the GPS.
I can also browse around the surrounding area too, which is handy for planning and orientation.
Also has the bonus of using a gadget I already carry with me, so I'm less likely to forget it!
travel.stackexchange.com/users/26/Gagravarr
A cheap unlocked Android phone with GPS (they start at $120 or so) plus a free offline maps app like RMaps .
You don't need a data connection, but have the option of popping in a cheap local prepaid SIM card for calls and net access.
Then you can use Mobile Atlas Creator 1.8 to download relevant maps from different sources before you go (or using a laptop and hotel WiFi while on the road).
travel.stackexchange.com/users/147/dbkk
MapDroyd gives you downloadable offline maps but this is limited to Android phones.
I tried this on my phone and did a comparison with Google Maps a year ago.
MapDroyd had quite a bit of work to catch up with Google.
travel.stackexchange.com/users/1883/Prashanth
For the iPhone, there's an app called Galileo that you can use.
It uses Openstreetmaps data.
You turn the caching feature on in the app, then when you're in the hotel, you navigate to the place you want to go, and grab all the data.
When you leave that place, you can purge the cache to free up space for the next city.
I found this to be really useful, since you can decide how granular you want your mapping data to be.
In some places, like say Hamburg, you're only going to be concentrating on a touristy portion of the city, not all of it, so you don't really need to download the other 95% in level 50 zoom.
travel.stackexchange.com/users/3686/Rog182
I don't need a recommendation or a list but my knowledge of GPS and "navi"s and the differences between them is an utter mystery to me.  But often I'm lost in backstreets in random countries where access to something like a live Google Maps would be awesome. I absolutely cannot afford a smartphone with worldwide roaming though.  Can GPS's do what I want or am I barking up the wrong tree? If they can is it only high end ones than can?
Are there cheap GPS or other navigator devices with downloadable maps for the whole world?
travel.stackexchange.com
<budget><gear><maps><gps-navigation>
travel.stackexchange.com/questions/448
travel.stackexchange.com/users/140/hippietrail
Ovi Maps, Rmaps and MapDroyd offer downloadable or maps that can be viewed offline on Android or other phones. Many smartphones will also allow you to cache maps locally and view them offline.  With Nokia devices like the Nokia Symbian you can get Ovi Maps and with the Nokia N900 you can cache maps locally. On the other hand, Unlocked Android phones with GPS give you the possibility to download apps like MapDroyd and Rmaps that provide offline maps.
With the Nokia Symbian you can get Ovi Maps and with the Nokia N900 you can cache maps locally. Unlocked Android phones with GPS give you the possibility to download apps like MapDroyd and Rmaps that provide offline maps.