Its happened to me a number of times and probably to some of your guys, and it always happens when I need it the most : no signal on my phone to use Google Maps!
Well Google is looking to help eradicate this problem and has today added a new feature to its Google Labs designed for Android Google Maps which will allow you to download maps for a specific area to your Android smartphone and view them within Google Maps.
The downloaded map can then be used on Android via Google Maps while visiting an unfamiliar location even when no data connection is available or drops out within an unreliable signal area. The new “Download map area” feature is still experimental at the moment and is currently available in Google Maps 5.7 for Android. More information is available over at the Official Google Blog Post.
Source : Google