i suppose you are using the built-in maps application? when it starts, just tap somewhere outside the pop-up that wants you to select a data connection. u might have to do this twice or three times as it keeps popping up. however, this way no data connection will be used. as already pointed out in this thread, it will take much longer to get an initial gps fix on your position.

usually, maps in the built-in maps application (ovi maps) are downloaded from the web as you go (at least on my device no maps, not even for my country, were preloaded). if you dont want that, you can download the maps for the areas you need to your computer beforehand and transfer them to your n900.

you can find maps for different regions here: http://www.hpsblog.com/2009/07/direc...0-without.html

connect your n900 to your pc via usb (as mass storage device). extract the files you have downloaded and copy them to the folder cities/diskcache on your n900.