If you want something user-friendly I'd recommend QuantumGIS:
http://www.qgis.org/
Its a very nice intuitive system, very good if you just want to add layers of data, make maps, and do some simple analysis - doesn't overwhelm you with possibilities like some systems. It can also do the more complicated stuff too if you need it to. Plus its open source, so doesn't cost anything.
Yes, Google Earth (GE) provides an excellent, easy to understand interface, for students learning about GIS (and other geospatial technologies). I teach an introduction to geospatial information technologies class and we begin with GE. Once the core concepts are understood, we move to other free software (Found in the book by Shellito): http://www.whfreeman.com/Catalog/product/introductiontogeospatialtechnologies-firstedition-shellito
At the end of the course we then dive into more advanced software like ArcGIS or Erdas Imagine (the students decide which tracks, GIS, GPS, or Remote Sensing to take).