Geographic calculators

Everybody knows about an excellent site GPS Visualizer with plenty of geographical utilities. I have been using it mainly for converting between various file formats (thanks to the equally excellent embedded GPS Babel tool) but recently I found its utilities for geographical calculations. I like its friendly user interface (allowing to copy easily data from one calculator to another one) and the gem, the "Draw range rings around a point".
 It allows me to see what actually I have loaded in my Garmin Oregon when preparing for a geocaching expedition. For example, In this map, each circle represents one GPX file in my Oregon.

More circles can be drawn together using another GPS Visualizer tool, the "Make a Google Map from a GPX File". Using the same tool, I can even see if the final coordinates of my solved puzzle geocaches fit in the range of the coordinates in my GPS:

Sometimes I need to find coordinates having a starting point, bearing (azimuth) and a distance. I often use http://www.movable-type.co.uk/scripts/latlong.html to do so:

 

It even shows you formulas how to make such arithmetic.