PHPSysInfo is valuable script to all web hosting companies.  This script is open source which means it will not even cost you a penny. What this script does is provide statistics and the current status of the server you are hosted on. It can display information such as, how many processors you have, how much Physical Memory (RAM) you have, how much of the hard drive is being used for each partition, and so much more. It also shows devices connected to your server and the current uptime of your server.

Prosoft Studio has used this script in the past and it was very helpful to us and our clients.  Although we do not use this script anymore, we highly recommend that everyone has at least something similar to it.

Here is the official description for the project page:

PHPSysInfo is a customizable PHP Script that parses /proc, and formats information nicely. It will display information about system facts like Uptime, CPU, Memory, PCI devices, SCSI devices, IDE devices, Network adapters, Disk usage, and more.

Project Page: http://sourceforge.net/projects/phpsysinfo/
Download: http://sourceforge.net/project/platformdownload.php?group_id=15