GPSBabel!

RouteConverter displays, modifies, enriches and converts GPS data between over 75 formats. It works without installation under Linux, Mac OS X and Windows, automatically detects the format of a file, supports drag and drop, undo and redo, offers a map view onto the positions of routes, tracks and waypoints, allows to modify positions in the map view, supports multiple routes within Google Earth, GPX and Garmin MapSource files, allows to select duplicate positions to remove them to abbreviate tracks, allows to move one or more positions of the route to the top, to the bottom, upwards and downwards, allows to complement elevation, place name, postal address, speed of positions from NASA SRTM3 and geonames.org, uses file and position names that suit to the display of the TomTom Rider, uses file, route and position names that suit to the display of the Map&Guide Motorrad Tourenplaner, remembers language, paths, window size and position »

With GPSies you can view and download tracks which have been recorded by a GPS device. Whether you are searching for running courses or Mountain Bike Tracks, with GPSies you can see what Tracks others have recorded. And you can download all the Tracks and put them onto your GPS device so you wont lose your way.

KMLCSV Converter is a free open source software that enables you to convert KML file to a formatted CSV file, and vice versa. This CSV file can then be uploaded into your Garmin GPS by using Garmin POI Loader, which can be downloaded for free. This allows you to easily plot all custom point of interests (POI) through Google Earth or Google Maps first before transferring them into your Garmin GPS.