A study of the magnetocaloric properties of manganites with ferromagnetic and charge-ordering states is presented. Under the application of a magnetic field in the vicinity of the paramagnetic-ferromagnetic and paramagnetic-charge order transitions large changes of the magnetic entropy are found, negative or positive, respectively. The physical mechanisms that contribute to the magnetic entropy and its temperature dependence are described and in the ferromagnetic case, discussed in terms of the Landau theory for phase transitions.