iStat Menus - "An advanced Mac system monitor for your menubar."
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.
Stats - Simple macOS system monitor in your menu bar.
Argus Monitor - Argus Monitor is for monitoring and analyzing the temperature and the health status of the hardware parts of the system.
smcFanControl - [Download] smcFanControl 2.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.