Core Temp is free and easy to use CPU temperature monitoring software. Displays core temperature in easy to understandable manner. Great tool helps us to keep an eye on your CPU Temperature to avoid Hardware failure.
iStat Menus - "An advanced Mac system monitor for your menubar."
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
Process Explorer - The top window always shows a list of the currently active processes, including the names of their owning accounts, whereas the information displayed in the bottom window depends on the mode that Process Explorer is in: if it is in handle mode you'l…
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.
MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)
CPU-Z - CPU-Z is a freeware that gathers information on some of the main devices of your system : Processor name and number, codename, process, package, cache levels.