Self-organized chains and stripes of silver nanoparticles have been elaborated by ion-beam sputtering shadow deposition onto faceted alumina substrates. We show that the in-plane organization of the silver nanostructures can be controlled through the grazing-incidence conditions (angle and orientation of the atomic beam with respect to the nanostructured surface). Their optical properties are dominated by a surface-plasmon resonance whose spectral position depends on the polarization of the incident light (parallel or perpendicular to the facets of the alumina template) and that can be attributed to a strong electromagnetic coupling between individual nanoparticles.