Nobody really provided a bunch of extra links to stuff, so here's some additional information and Wikipedia links on technology actually implemented in shuttles:
A reaction wheel (RW) is a type of flywheel used primarily by spacecraft for attitude control without using fuel for rockets or other reaction devices. They are particularly useful when the spacecraft must be rotated by very small amounts, such as keeping a telescope pointed at a star. They may also reduce the mass fraction needed for fuel. This is accomplished by equipping the spacecraft with an electric motor attached to a flywheel which, when its rotation speed is changed, causes the spacecraft to begin to counter-rotate proportionately through conservation of angular momentum. Reaction wheels can rotate a spacecraft only around its center of mass (see torque); they are not capable of moving the spacecraft from one place to another (see translational force). Reaction wheels work around a nominal zero rotation speed. However, external torques on the spacecraft may require a gradual buildup of reaction wheel rotation speed to maintain the spacecraft in a fixed orientation.
CMGs differ from reaction wheels. The latter apply torque simply by changing rotor spin speed, but the former tilt the rotor's spin axis without necessarily changing its spin speed. CMGs are also far more power efficient. For a few hundred watts and about 100 kg of mass, large CMGs have produced thousands of newton meters of torque. A reaction wheel of similar capability would require megawatts of power.
This, combined with monopropellant and other such types of limited propulsion come together to create a full RCS.
A reaction control system (RCS) is a spacecraft system that uses
thrusters to provide attitude control, and sometimes translation. Use
of diverted engine thrust to provide stable attitude control of a
short-or-vertical takeoff and landing aircraft, below conventional
winged flight speeds, such as the Harrier "jump jet", may also be
referred to as a reaction control system. An RCS is capable of
providing small amounts of thrust in any desired direction or
combination of directions. An RCS is also capable of providing torque
to allow control of rotation (roll, pitch, and yaw). RCS systems often
use combinations of large and small (vernier) thrusters, to allow
different levels of response. Spacecraft reaction control systems are
used: for attitude control during re-entry; for stationkeeping in
orbit; for close maneuvering during docking procedures; for control of
orientation, or 'pointing the nose' of the craft; as a backup means of
deorbiting; as ullage motors to prime the fuel system for a main
engine burn. Because spacecraft only contain a finite amount of fuel
and there is little chance to refill them, some alternative reaction
control systems have been developed so that fuel can be conserved. For
stationkeeping, some spacecraft (particularly those in geosynchronous
orbit) use high-specific-impulse engines such as arcjets, ion
thrusters, or Hall effect thrusters. To control orientation, a few
spacecraft, including the ISS, use momentum wheels which spin to
control rotational rates on the vehicle.
Also, for those who play KSP and wonder how realistic those wheels are:
The other big difference is that KSP's reaction wheels are absurdly
effective compared to their real-world counterparts. Real-world
reaction wheels generally can't send a craft from zero to "vomit
comet" spin speed in 5 seconds flat the way even a single reaction
wheel in KSP can.
Even more resources for turning in space: