QGIS is available for download for Mac, Windows and Linux. No license is required, as it is free and open source.
As of August 2014, QGIS Desktop is available in version 2.4. Earlier versions are also available.
Online Documentation and Tutorials
Includes the "QGIS Training Manual" (with canned data and exercises, enough for a 5-day workshop!), and the concept-oriented "A Gentle Introduction to GIS"
Great content, much of it focused around examples with non-Roman character sets, and using other open source tools like LibreOffice
Also includes excellent installation instructions
Published in 2013, by Anita Graser. Available online to UM affiliates