If you are looking for a company based network monitoring software package i "highly" recommend Solarwinds Orion Suite. I have been using it for a while now and it makes my job so much easier. Its a little pricey but you get what you pay for.
Looking for a good network monitoring software. Free would be great but has anyone compared the various types and discovered a good one?
I can recommend one that I've been using for about a year now, and I find it very satisfying. It does exactly what I need it to do: it monitors my employees by showing me when they signed on and off work, it counts the keystrokes and mouse clicks made during their work-hours, and takes screenshots every several minutes. It is called My Team Monitor, and it is free. You just need to register at their site www.myteammonitor.com
I've been using for over a year Pandora FMS and I think the easiest tool to manage. I tried OpenNMS, Cacti and Nagios and I seem more difficult to use and not as complete as PandoraFMS (www.pandorafms.com). You can monitor remotely through ICMP, TCP, SNMP and locally installing pandora agents. It's free and unlimited.
Other good option is PRTG Network Monitor (www.paessler.com/PTRG) but its free version is very limited. and haven't got local monitoring.