Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
Process Tamer - Freeware Microsoft Windows utility that monitors the CPU use of applications, alerts when they use too much, and reduces their priority to keep your PC fast.
GPU-Z - GPU-Z is a lightweight system utility designed to provide vital information about your video card...
Big Meter Pro - Big Meter Pro is a utility that monitors the disk and memory of your CPU.
iStat Menus - "An advanced Mac system monitor for your menubar."
AMD Overdrive Utility - Personalize your experience with state-of-the-art real-time overclocking*.