WGS84 Geodesic Calculator
Calculations supported are inverse, direct, perpendicular intersect, bearing-bearing, distance-distance, arc length, geodesic arc intercept, and many more. Currently in early development.
GeoEngineCom - Coordinate Projections
Easily add coordinate transformation and projections to your applications using ActiveX and the C GeoTrans source code from the National Geospatial Intelligence Agency.