We give an overview of the development of discontinuous Galerkin methods for incompressible flows. We begin with the application of discontinuous Galerkin approximations of second-order elliptic operators. We provide a framework for the analysis of a large class of discontinuous methods for these problems which allows for the understanding and comparison of most of the discontinuous Galerkin methods that have been proposed for the numerical treatment of elliptic problems by diverse communities over three decades. We also present numerical comparisons of these methods. We then consider discontinuous Galerkin methods for the Stokes, Oseen and Navier-Stokes equations.