A few years ago (ok a LOT) I had written a VERY simple network monitoring system for work. It primarily gathers syslog events, and does a basic TCP connect to check on machine state. This uses MSDE as it's engine for events.
Apache VirtualHost Transfer Counter is a set of files which allow you to quick and easy monitor utilization of http bandwitch on your server. It can give you also few statistics about VirtualHosts.
Visual Network Manager (VNM) software manages your critical network assets across your entire infrastructure, integrating disparate data from multiple vendors, protocols, and legacy systems into a single web portal.