iGPS is a good companion for anyone wanting to save their routes and waypoints from their GPS onto their Mac.
The program actually works both ways, so you can receive data from your GPS and save it to your Mac or send data to your Garmin GPS. You'll need to make sure you have a USB to serial adapter to connect your GPS to your Mac to be able to use the application.
iGPS lets you choose whether you want to send or receive only waypoints, routes or both types of elements. Thanks to the drop down menus you can choose exactly which waypoint or route you want to select. You'll be able to save the information in GPX format which can then be read by any Garmin GPS device.
The trial prevents you from saving and sending to different GPS so you'll only be able to try it with one device.
iGPS makes receiving and sending GPS waypoints and routes to and from your Mac really easy.