MenuBar Stats - Advanced Mac system monitor right from the menu bar
iStat Menus - "An advanced Mac system monitor for your menubar."
MenuMeters for El Capitan - MenuMeters for OS X El Capitan 10.11 (and later)
Stats - Simple macOS system monitor in your menu bar.
iPulse - Using its concise and appealing user interface, iPulse graphically displays the inner workings of macOS on you desktop, menu bar or Dock.
Rooster - Local sharing community where neighbors share free resources