Datum Pro http://www.datumpro.linden-software.com/
Software application that does datum transformations. Converts individual positions between over 400 datums to or from user specified TM and UTM grids.
James Q. Jacobs - Geodesy Page http://www.jqjacobs.net/astro/geodesy.html
Definitions relating to geodesy, explanations of coordinate systems, and geodesy formulas. Reference ellipsoid defined with derived geometrical constants, equation of the meridional ellipse, and geometry of the meridian section.