MSI Afterburner - Tool to manage video cards. Shows video card stats (temp, GPU usage, etc.).
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.
ASUS GPU Tweak - ASUS GPU Tweak fully implements TechPowerUp’s GPU-Z analysis and monitoring features.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
Geforce Experience - GeForce Experience is a new application from NVIDIA that optimizes your PC in two key ways.
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.