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 bénard problem -- Weighted energy methods in elastostatics on unbounded domains -- Weighted energy methods in linear elastodynamics in unbounded domains.