Having said that, if you have MapSource, you can save your waypoints file as a gpx and then load it to your GPSr as Custom POIs. They provide the software to load them and the firmware that accepts them, but the creation of the Custom POIs isn't something they get into directly.
First of all, Garmin considers Custom POIs to be basically a third-party item. If you haven't heard about this site, check it out. It's a very simple interface and allows you to create your own POI's or add to a POI to an existing POI on your GPS. I found and with a few clicks was able to locate the street I was looking for and then was able to name it and load it into my Nuvi. Long story short, the street name was a bust, every time I tried to enter it. I was looking for a cousins address in Florida, on my Nuvi 670. Hi All, This may be old news for many, but as a newbie to creating POI files, this site allows me to create or edit my own POI files. You can download EasyGPS and use it to make Custom POI files. These are basically waypoints, but considered to be a Custom POI.
This set of applications will help you create customized points of interest within your navigation device. A point of interest (POI) is a definite geographic location that someone may find useful or interesting. Free Customized POI Creator Free Downloads.