Using the plasmon hybridization method, we investigate the plasmon frequencies and optical absorption spectra of symmetric configurations of nanosphere trimers and quadrumers. Plasmon hybridization allows us to express the fundamental plasmon modes of these multinanosphere systems as linear combinations of the plasmons of individual nanospheres in a manner analogous to molecular orbital theory. We show how group theory may be used to interpret the plasmon modes of each multiparticle system as specific structure-dependent symmetric combinations of the plasmon modes of the individual nanoparticles. We compare the optical absorption spectra calculated using plasmon hybridization with the spectra obtained using finite difference time domain simulations.