Openjump

* It is a Vector GIS that can read rasters as well.
* OpenJUMP is known to work on Windows, Linux and Mac platforms, but
  should work on any operating system that runs Java 1.5 or later.
* It is not just another free demo viewer, but you can edit, save,
  analyze etc. with JUMP / OpenJUMP.
* It works, even with medium size datasets, and with professional
  touch.
* It provides a GIS API with a flexible plugin structure, so that
  new features are relatively easy to develope around the sound
  mapping platform.
* It utilises standards like GML, WMS and WFS.
* It is already translated in English, Finnish, French, German,
  Italian, Portugese and Spanish. The translation in other languages
  is in progress.