The properties of polymer nanocomposites exceed the properties of common composite materials due to the nanoscale size and morphology of the fillers used. Particulate fillersare commonly used in polymers forimproved mechanical and thermal properties, as well as modified electrical properties and cost reduction. Organically modified layered clays, such asmontmorillonite, are among the most widely used fillers for the improvement of polymer matrices. Presented in this review are some of the most studied clay nanocomposites including clay-polyolefin, clay-polyester and clay-thermoplastic polyurethanenanocomposites. Additionally, the properties of clay-biopolymers nanocomposites will also be discussed.