Load My Tracks.
Using Load My Tracks I can pull my GPS tracks right off my device and save them for use by other applications: GPX files, even KML for use with Google Earth. Load My Tracks supports geocaching and a pretty good range of devices.
But while looking into Load My Tracks, I also found some more resources:
Here is a list of GPX resources. It is a pretty good list, and covers multiple platforms (Windows, Macintosh, Mobile, and cross-platform).
Some other applications that I have not tried, but I am including here in case they might be something you can use:
GPS Connect: A Freeware Garmin GPS Connection Tool for Mac OS X.
Mac SimpleGPS: a Macintosh application designed to manage waypoints, routes and tracks on your GPSR.
Between these links, and my previous post, you should have more than enough to get you started with however you would like to use your GPS device with Macintosh computers.