Pennock's GPS Viewer

One of the nice things about this program is that it actually projects the received satellites onto the map, along with your current position of course.

It's nice to see where in fact the satellites are. You can also customize PGV with your own maps. PGV supports "Normal Projected" maps (or "Flat Maps") and "Miller Projected" maps.
Right now, PGV only works with USB and serial NMEA compatible receivers.