MSI Afterburner - Tool to manage video cards. Shows video card stats (temp, GPU usage, etc.).
Guru3D - Guru of 3D: PC Hardware Reviews and tests
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
NVIDIA Inspector - Nvidia Inspector is a small and handy tool that displays hardware information for Nvidia-based...
PowerStrip - PowerStrip provides advanced, multi-monitor, programmable hardware support to a wide range of...
FPS Monitor - FPS Monitor tracks your PC's hardware state and displays this information as an overlay in-game.