Xastir

http://www.xastir.org/ -- "Xastir provides mapping, tracking, messaging, weather, weather alerts, and Search & Rescue features over radio or internet and runs on a variety of platforms. Xastir is an open source software project maintained by Developers and Contributors from all over the globe, provided free under the GNU General Public License. From its early beginnings, Xastir has evolved into a very robust client with a rich feature set that rivals other APRS clients. "

On my Mac

The recommended way to run Xastir on a Mac is in a virtual machine. Okay, I can do that. But I am going to try it in a Debian 7 machine under Parallels instead of downloading their complete VMWare Fusion machine. While waiting for it to download I will look up what map data I need.

I set Debian up with Cinnamon. Then I installed KDE and tore out Cinnamon, so that Coherence would work.

I followed the instructions to build Xastir from source, which I found here: http://xastir.org/index.php/HowTo:Debian_Squeeze

It was easy to build it from sources. I have it running now with the opencyclemap.

With a GPS

I installed gpsd and then did

Interface->Add->Network GPS and accepted the defaults (localhost). Then I did "Start All" and sure enough my position jumped from the coast of Africa (0 0) to my house. Joy.