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.
The Dude - MikroTik is a Latvian company which was founded in 1996 to develop routers and wireless ISP systems. MikroTik now provides hardware and software for Internet connectivity in most of the countries around the world.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
Pandora FMS - Pandora FMS: Opensource monitoring software
Macs Fan Control - Macs Fan Control is an iMac, MacBook Pro, MacBook Air, Mac Mini and Mac Pro fan control that is the solution of two basic issues namely noise problems and overheating problems.
cStatus - Monitor and scan a network.