I just found this yesterday and thought I'd share for those that are not aware. Particularly when people ask for GPS suggestions a lot. Apparently in Google Maps (on my phone), if you go to More->Labs, you can find Pre-Cache map area. What it will do if you select an area, one of your options will to pre-cache a 10-mile grid of the area. Haven't tested it yet to see if it actually works well, but should be useful for people like me that don't have a data plan on their phone right now, people with tablets that have GPS and possibly an iPod touches as well (I don't know if they have GPS). Also useful when you go in an area where service is practically nonexistent.