Well, the second and third posts of my GIS tutorial covers the basics of doing this in QuantumGIS which has a specific tool for making such symbols: http://www.cartographersguild.com/sh...-for-using-GIS

A vector graphics editor like Inkscape or Illustrator is also well suited to such a task. By using linked clones you'll have a lot of the same ability to tweak symbols after placement that a GIS has. They also generally have handy options like "Snap to Object Centre" to make drawing concentric shapes easy.