CPU Frequency Selector - Cinnamon CPU Frequency Selector Applet
SysGauge - SysGuage is a responsive software utility that monitors the memory status, CPU usage, as well as network and disk activities of your system.
Udev Discover - A helping tool for udev testers, coders, hackers and consumers.
Big Meter Pro - Big Meter Pro is a utility that monitors the disk and memory of your CPU.
CPU-Z - CPU-Z is a freeware that gathers information on some of the main devices of your system : Processor name and number, codename, process, package, cache levels.
Process Lasso - Process Lasso is NOT yet another task manager.