CleanMyMac X - Clean, protect and speed up your Mac
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.
MacKeeper - The new MacKeeper app delivers multilayered protection from malware, online threats, and identity theft & Mac performance optimization. Learn what is MacKeeper.
Open Hardware Monitor - Monitors temperature sensors, fan speeds, voltages, load and clock speeds, with optional graph.
MacCleaner Pro - MacCleaner Pro is a bundle of 6 apps to clean up disk space and speed up Mac.
xScan - xScan is an application for viewing the behavior of your computer and Mac.