Yes, it's possible to preload google map data so it can be used without any connection. It used to be necessary to enable this under Settings > Labs, but they've actually built this feature right into Maps this year.
Here is the Google support page with instructions on how to preload areas:
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Here is the Google support page with instructions on how to preload areas:
http://support.google.com/gmm/bin/answer.py?hl=en&answer=2650218