Points of Interest or POIs are locations that are part of, or can be added to, GPS devices. A POI could be a gas station, a hotel, a restaurant, a shopping mall, or a historical location.
The data for the POI databases is collected from a variety of sources. In some cases the mapping companies compile it, sometimes the data is provided directly by larger chain locations, often times the information is gathered by companies who specialize in creating business directories. Sometimes they are even compiled by people with a special interest like RVers who create POIs of their favorite RV parks.
The data typically includes the physical address, name of the location, category of the POI, a phone number, and the geographic coordinates.
RVbasics.com Yahoo Group member Jon offers his top 5 POI databases.
In my experience as a driver, here are my top 5 POI databases for you to download for your GPS. (Free & paid).
Speed cameras
http://www.gps-data-team.com/poi/united_states/safety/Speed_Trap.html
Low clearances
http://www.lowclearances.com
Truck stops
http://www.poifriend.com/poigroup.php?poigroup_id=6749
Gas stations
http://www.gps-data-team.com/poi/united_states/petrol/
Walmart
http://www.poifriend.com/poigroup.php?poigroup_id=406
I have all of these installed and they all work really well.