DaisyDisk - DaisyDisk is a disk analyzer tool for OS X that visualizes hard disk usage and allows to free up hard disk space.
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.
CleanMyMac X - Clean, protect and speed up your Mac
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
MacFly Pro - Smart assistant for better Mac performance
iMac HDD Fan Control - iMac HDD Fan Control is an HDD fan control for the Mac operating systems by using which the Mac users can control the speed and noise of the fan of the Mac.