Mega GPS The Online GPS Superstore
Offers Garmin GPS units and accessories at substantial discount. My own experience with them has been excellent. Screen Reader usable, but not especially friendly.
NAVTEQ Maps and Traffic Information
NAVTEQ is one of two companies that actually makes the maps used in GPS and other map resources. If you need to make the map makers aware of changes in your area that are not showing up, this is one place to start.
What 3 Words
This system allows any location to be described using only 3 words. These may be easily remembered and passed to any other person. They may be than used to locate a specific location on a map. An app is available for most smart phones.