Geomagnetic Data at NGDC
Determine magnetic declination for any latitude or longitude and date from the National Geophysical Data Center in Boulder, Colorado. Online calculations or download the software. The only way to go!

NGS Survey Software
Thirty PC software packages for surveyors, includes: Inverse/Forward3D, Geoid93, Adjust (least square adjustment), NAD27 to NAD83 transformation, Loop closure and more.

National Geodetic Survey Data Sheets
Locate Data Sheets within a two mile radius of a given latitude/longitude. Searches until it finds at least 20. A must for surveyors.

Land Surveying Information
Ted Rollheiser, PLS, has knock himself out to give you all those, "Cool Surveying Sites"