This chapter explains the origin of surface plasmons and the relative magnitude of various parameters on the values of plasmon frequency. It describes the synthesis and processing of various kinds of metal nanoparticles using colloid chemistry methods, with the objective of achieving a high degree of control of the optical response, derived from surface plasmon manipulation. The chapter starts with nanoparticles containing both gold and silver, focusing on the different effects derived from the distribution of the metals. It turns to shape effects, starting with the possibility to modulate the optical response of gold nanorods through nanorod alignment and illumination with polarized light, which in turn serves to introduce various examples of linear assemblies of nanoparticles using carbon nanotubes, showing either isotropic or anisotropic interparticle interactions. The chapter discusses optical effects due to interparticle interactions in multilayer films of gold nanoprisms. The assembly of nanoprisms is expected to lead to interactions, which depend on the actual morphology of the assembly.