Great Circle Distance Calculator
Calculate distances using great circles, NOT road distances!
Decimal Degrees to Degrees, Minutes, and Seconds
Converts between decimal degrees and degrees/minutes/seconds and back again
Coordinate Conversion -- GSRUG Online Computation
Converts latitude/longitude to UTM and UTM to latitude/longitude. From Natural Resources Canada
Mathematical Data for Bibliographic Descriptions of Cartographic Materials and Spatial Data
Conversions, definitions, and source materials for bar scales, measurements, prime meridians, and coordinates. Compiled by Jan Smits, Map Curator Koninklijke Bibliotheek.
Online Distance and Length Conversion
Convert modern and ancient distance measures.
Cartographic Reference Resources
Among other resources, includes map projections and map scales. Compiled by the map library at the University of Texas at Austin.