SpeedFan - Hardware monitor for Windows that can access digital temperature sensors located on several 2-wire SMBus Serial Bus. Can access voltages and fan speeds and control fan speeds. Includes technical articles and docs.
Total Network Inventory - Total Network Inventory is a piece of software designed to help with managing software inventory and auditing PC systems.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
Lansweeper - Lansweeper discovers Windows, Linux and Mac machines in your network.
xScan - xScan is an application for viewing the behavior of your computer and Mac.
Kuwaiba - Kuwaiba is an open source, enterprise grade network inventory and CMDB for your telecommunications and IT infrastructure