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.
Razer Cortex - A free all-in-one software which gives you the best gaming experience, featuring best gaming deals, PC and Mobile Game Booster, and more!
smcFanControl - [Download] smcFanControl 2.