Quantum GIS (QGIS) is an extensible GIS application. This means that we can add more features or functionality to QGIS. The easiest way is by adding or installing more plugins to QGIS.
There are many plugins available to install. They are growing and many more plugins to come and updated. In order to add plugins ot QGIS, go to Plugins | Manage and Install Plugins. You can select the plugins from the list to be installed.