The latest release of QGIS 2.4, called Chugiak, is now available for downloading. QGIS is a freely available GIS software program.
QGIS now supports multi-threaded rendering! What this means is that when drawing the map, QGIS will split the drawing work between all of the cores in your CPU, making the process more efficient and responsive. By responsivewe mean that you no longer need to wait for the map view to update before you can pan or zoom again. Also the map display updates incrementally allowing you to see if the map is positioned correctly early on in the drawing process. Take a look at this article for a more detailed overview of the multi-threaded rendering system. You will find some options in the QGIS settings dialog that allow you to manage the behaviour of multi-threaded rendering.
Also, the composer which is used for creating print ready maps, has many updates one of which is the ability to simulate what maps will look like if they are faxed, photocopied (grayscale) or viewed by a color blind person.
Source: GIS Lounge
