Declination Compass uses the World Magnetic Model (WMM) to calculate the magnetic declination for any give point on the earth. The compass will work for your current location, or you can enter in a location and altitude and the compass will give you the declination for that point.
Caution: While Declination Compass tends to be extremely accurate for most places on the earth, there are many factors that affect magnetic declination and any magnetic model can be subject to errors caused by those factors.
Icons courtesy of Gliphish http://www.glyphish.com/