Stock Google Maps
Depending on the version you have, stock Google Maps can cache maps for offline use. If you're using the (slightly) older version, you can do it easily by pressing the menu key, selecting Make Available Offline
and selecting the area you want to cache.
If you're using the newest Maps, you'll notice the option is gone. Instead, you'll have to zoom in over the area you want to cache, and type in "ok maps" into the search bar and press enter/go. A translucent dialog at the bottom of the screen should appear notifying you that the map has been cached.
Once cached; you should not require a internet connection to use maps. Though I have never actually used it offline, so I am not entirely sure what the experience is like. Also note that this does not save satellite/aerial imaging. Only navigational maps.