Convert   A windows freeware program that performs numerous unit conversions including distance, speed, temperature, energy, flow, force, computer storage, and more.

UTM-Lat/Lon Conversion DOS based BLM bi-directional UTM-Latitude/Longitude conversion program (NAD, 1927)

State Planes-Lat/Lon Conversion DOS based BLM bi-directional State Plan or Latitude/Longitude conversion program.

MICRODEM  Website offering free software to handle, display and merge electronic maps; also with conversion routines between NAD27 and NAD83 as well as other world coordinate systems.

Corpscon Another website offering free software for coordinate conversions in various coordinate systems.