Observium is an autodiscovering SNMP based network monitoring platform written in PHP which includes support for a wide range of network hardware and operating systems including Cisco, Linux, HP, Dell, FreeBSD, Juniper, Brocade, Netscaler, NetApp and many more.
Observium has grown out of a lack of network monitoring platforms which are both simple to manage and pleasant to use. It is intended to provide a navigable interface to the health and performance of your network. Its design goals include collecting as much historical data about devices as possible, using as much auto-discovery as possible with little or no manual intervention, and having a very intuitive interface.

Ralph is an asset management system for your data center.
It lets you see what hardware and software is installed. It also lets you keep track of who is using every device, what is it used for and how much it costs.