A Linden (which varies at any given time) assigned to care for the grid. The duties of a Grid Monkey (generally typed without the space, e.g. GridMonkey) include keeping an eye on problems that prevent the grid from running, and inspecting problematic simulators.
There usually is a Grid Monkey on-call at all hours of the day/night, making sure someone is ready to take care of any issues at all times.
For previous gridmonkeys, please see Category:Previous Grid Monkeys