We present optical spectrophotometric observations for 50 blazars obtained in 13 different campaigns over a 7 year period. The spectral flux distribution is studied in terms of a power-law (fnu varies as nu exp alpha) and, when relevant, the contribution of a host galaxy. We give spectral indices and fluxes of the nonthermal component and, when detectable, the absolute magnitude of the host galaxy. For more than half of the objects we obtained sufficient observations to study the relation between spectral index and flux level.