Spiceworks - how can they offer this for free?

Spiceworks is an IT inventory management system that will let you keep track of every system on your network. You can generate reports and troubleshoot problems on multiple systems from one control center. The only downside is that while you can monitor Unix and Linux systems, you can't install and run Spiceworks from them. Still, the trump card is the price - there isn't one.

Get it here