Free Geographic/UTM Coordinate Converter and Datum Transformations

Geographic/UTM Coordinate Converter is a online tools for coordinates convertions. You can convert between geographic coordinates and Universal Transverse Mercator (UTM) coordinates using  form that available on this site. With Coordinate and Datum Transformations you can convert coordinates between a variety of geodetic datums

GARNIX a scriptable coordinate conversion tool

GARNIX is a communication program that provides data interface between MS-DOS/Windows/Linux/OSX computers and a GARMIN GPS device .
GARNIX also open source appplication with scriptable coordinate conversion tool  that can converts lon/lat, ECEF und TM (Gauss-Krüger) coordinate systems , and GARNIX works with a variety of GARMIN GPS receivers.

Licences is Free (GNU licence)

Download here coordinate conversion tool