I am taking an introductory course in GIS at my university and my teacher recommended QGIS for Mac users. Unfortunately, I haven't been able to download the software. I just upgraded to Mac OS 10.8.2 recently, and I am not sure if Lisboa can work on Mountain Lion. Please let me know what I need to do in order to run QGIS on my laptop.
Go to http://www.kyngchaos.com/software/qgis (as described above) and download the following - my list are the minimal requirements to run QGis on 10.8.2 ML.
Open the .dmg´s and install it in the given order (at point 1 use only the installer GDAL complete installer (can´t remember the exact name).
If Gatekeeper say you are not allowed to install this software go to Systempreferences => Security and change the settings for the moment. During the above installation you are prompted 3 times for your Admin password. At the end you will find a new icon (the yellow Q) in your application folder (it is also available using Launchpad).