In QGIS there are 100’s of plugins available. One of the best I have used is the SEXTANTE plugin. You can download this by going to Plugins>Fetch Python Plugins and search for SEXTANTE.
Once downloaded it should create it’s own menu called Analysis. I just clicked SEXTANTE toolbox and this is what it looks like.
SEXTANTE can be literally thought of a as toolbox. It has almost everything you need. In the options you can choose to turn on the listed tools. Some of the options are modeler, the QGIS tools such as interpolation and DEM analysis are included. Tools for LiDAR database management, creating scripts and the list goes on.