IT Infrastructure Management using open source tool

I need an article about 1000 words and graphs and pictures to cover following points -Few open source and completely free tools to manage IT Infrastructure a. Network Management Tools (Cacti, mrtg, Nagios, PRTG, OpenNMS) b. Server Management Tools (Hyperic HQ, Zabbix) c. Backup Management Tools (FreeNAS) d. Inventory/Asset Management Tools ([login to view URL] with GLPI) e. Visitor Management Tools ([login to view URL]) f. Printer Management Tools g. ID Management Tools (Open LDAP) h. VoIP Tools (Asterisk, FreePBX, FreeSwitch) i. Messenger Tools (Jabber) Basically the idea is to help new IT Managers and IT administrators to manage IT infrastructure using opensource tools to reduce the cost of operation. The Article should cover brief about tools available for various IT Infrastructure components. It should give few examples of the global organisation that have benefitted using open-source tools.