In this article we study models with non-clearing markets in a full general equilibrium framework. The theories we describe synthesize three major schools of thought, Walrasian, Keynesian and imperfect competition. This synthesis is notably achieved by introducing quantity signals in addition to price signals into the traditional general equilibrium model. This considerably enlarges the scope of traditional general equilibrium, allowing us not only to construct equilibria with various price rigidities but also to endogenize prices in a decentralized imperfect competition framework.