The Dude (http://www.mikrotik.com/thedude.php) is...
Quote...a visual and easy to use network monitoring and management system designed to represent network structure in one or more crosslinked graphical diagrams, allowing you to draw (includes automatic network discovery tool) and monitor your network however complicated it might be. The Dude is capable of monitoring particular services run on the network hosts, and alerting you about any changes in their status. It can read statistics from the device monitored and show you graphs of the monitored values, allows you to test and connect to the devices easily, and provides some very basic RouterOS configuration tools.
And very useful it looks too. First, though, I need to read all about it (http://wiki.mikrotik.com/wiki/Dude_usage_notes)!
Did I mention the price?
QuoteThe Dude is free of charge!