Anyone used OpenCPN - looks quite interesting ....
http://opencpn.org/
Seems targeted for sailing, but:
Features
BSBv3 raster and S57 ENC chart support.
CM93 vector chart support.
IHO S52 compliant display of S57 vector charts.
Single-chart and Quilted display modes.
North-up, Course-up and Skewed-up display modes.
Moving-map display mode.
Route navigation with ship tracking functions.
Waypoint navigation.
Dashboard for configurable on-screen display of ship's NMEA data.
NMEA 0183 GPS interface at selectable baud rate.
gpsd library support.
Autopilot output support.
AIS input with full target tracking and collision alerting.
Anchor watch/alarm functions.
GRIB file input and display for weather forecasting.
GPX Waypoint, Track and Route input and output file support.
Tide and Current prediction and display by location.
Multi-language support.
Platforms
* Windows 98,2000,XP,Vista,7
* Linux, BSD, Solaris
* Macintosh OSX
and it's free!