From Ewert Technologies:
UTM Coordinate Converter, converts between various geographic coordinate systems, allowing you to convert between various Latitude/Longitudes systems and the Universal Transverse Mercator (UTM) system. It includes a map that displays the location you converter, as well the map allows to select a location you would like converted (see Features for more details). The converter supports converting between locations in Decimal Degrees, Degree Minutes, Degree Minutes Seconds and UTM. The following UTM Datums are supported: NAD83/WGS84, GRS80, WGS72, NAD27, GDA94, AGD84, ED50, OSGB36, Krasovsky 1940 and Everest 1830. UTM Coordinate Converter uses OpenStreetMaps, and supports Mapnik, OSM Cycle Map, Bing Aerial Maps, MapQuest-OSM, and MapQuest Open Aerial.