I like this article, cause it uses a simple tool, nmap, and a script to basically look for some issues you may have on your network. This could be a good cheap way to automate looking for issues on your network. Note you have to get the addition at http://www.computec.ch/mruef/software/nmap_nse_vulscan-1.0.tar.gz.
http://isc.sans.edu/diary/Using+nmap+scripts+to+enhance+vulnerability+asessment+results/16090