Introductory topics on stability of viscous flows.- Energy methods in unbounded domains: The case of a half space.- Energy methods in unbounded domains: The case of an exterior domain.- Some properties of steady solutions in exterior domatins.- Exchange of stabilities, symmetry and the connection between linear and nonlinear stability.- Skew-symmetric operators and nonlinear stabilization: The hydromagnetic b¿rd problem.- Weighted energy methods in elastostatics on unbounded domains.- Weighted energy methods in linear elastodynamics in unbounded domains.