(This blog is in reference to a Debian Lenny AMD64 system)
hp-health is the package that is supposed to provide access to the fan status on HP Proliant servers.  It is not easy to install hp-health on Debian Lenny.  The ISO can be located by searching the HP website.

On my system the existence of 2 files for UPS monitoring software Winpower causes ldconfig error messages:
/usr/lib/libjspTru64Alpha.so
/usr/lib/libjspAixPpc.so
 – you can try to temporarily move the files during installation/removal of hp-health, but this didn’t help due to the following errors.

Having VMware Server 2 installed confuses the hp-health init script (/etc/init.d/hp-health), which is designed to have different behaviour for ESX servers.  Applying an exit workaround in the procedure causes the script to appear to behave correctly, but the daemon fails to start.

Uninstallation of hp-health is also fraught with difficulty. It is necessary to alter the exit code on the init script just to get the script to continue with removal.  The script will fail to remove /opt/hp/hp-health (and will attempt to remove /opt !).  If you need to manually change the installation status you will need to edit /var/lib/dpkg/status to remove the hp-health section.

After doing all the work above it was found that ipmitool could easily be installed:

apt-get install ipmitool
modprobe ipmi_msghandler
modprobe ipmi_devintf
modprobe ipmi_si
  And the fan RPM's are shown with:
ipmitool sdr type fan

(it takes a few seconds to probe).