By using feedback control techniques a variety of plasma instabilities have been suppressed. In all cases these instabilities have long wavelengths, low azimuthal wave numbers, and simple radial dependence. This minimizes control problems associated with the spatial variation of the mode. Drift waves, gravitational flutes, ion sound waves, Kelvin-Helmholtz 'edge oscillations', and other instabilities have been feedback stabilized using a variety of control systems. This review attempts to illuminate the problems of feedback control in plasmas by a study of the work in this field.