In this book two different disordered systems are studied: the SK-model (with its fermionic counterpart the fermionic Ising model ISGf) and the Coulomb-glass. Both models are known to exhibit a glass phase and a pseudo-gap around the Fermi-level, and the work will focus on different aspects of their pseudo-gaps. For the famous SK-model new numerical results using Replica Symmetry Breaking are obtained and a new fit routine is presented. The Coulomb-Glass (CbGl) is investigated by analytic calculations following work done by Müller and Pankov. By investigating these models this book gives detailed examples of a variety of mathematical tools used in modern theoretical solid state physics dealing with disorder. The Replica Symmetry Breaking scheme is applied for numerical calculations with a parallel algorithm, a discrete theory is transformed to continuous field theory allowing path-integral calculations and approximations like the locator approximation are used.