Quantum GIS (QGIS) is a user friendly Open Source Geographic Information System (GIS) licensed under the GNU General Public License. QGIS is an official project of the Open Source Geospatial Foundation (OSGeo). It runs on Linux, Unix, Mac OSX, Windows and Android and supports numerous vector, raster, and database formats and functionalities.
QGIS is available on Windows, MacOS X, Linux and Android. Binary packages are provided for the current version. The current version is QGIS 1.8.0 and was released in June 2012.
Quantum GIS is open source software available under the terms of the GNU General Public License meaning that its source code can be downloaded through tarballs or the git repository.
Redhat, Cenots and Fedora
QGIS 1.8.0 is available in Redhat,Fedora 16 and 17. Fedora splits QGIS into 4 packages: qgis, qgis-python, qgis-grass and qgis-mapserver.
# yum install qgis qgis-python qgis-grass qgis-mapserver
The pound sign (#) indicates, that you must run yum as the root user. Don't type the pound sign!
A newer version might be available in the testing repository -- usually around one week:
# yum install --enablerepo=updates-testing qgis qgis-python qgis-grass qgis-mapserver