This talk will overview the interplay between optics, plasmonics, and excitonics for systems that consist of arrays of gold, silver or aluminum nanoparticles in 1D, 2D and 3D. This will begin with a review of the use of classical electromagnetic theory to describe the optical properties of plasmonic particles of arbitrary shape, size and arrangement, and which leads to a variety of enhanced spectroscopies including surface enhanced Raman scattering. Then I examine two kinds of arrays, those involving DNA-linked nanoparticles with subwavelength particle spacings, and those involving 2D arrays of particles where the spacing satisfies a diffraction condition that produces lattice plasmon resonances. The emphasis of the DNA—linked nanoparticle structures will be on describing scattering and extinction experiments where issues such as effective medium approximations and Fabry-Perot cavity modes are important. I also describe DNA-linked structures with embedded dyes, and structures that exhibit nonreciprocal properties. The studies of lattice plasmons include unusual extinction and scattering properties of the lattices that include quadrupole resonances effects for aluminum lattices, and lattice plasmon lasers in which laser dyes are added to the nanoparticle lattices and where the theory needs to combine electrodynamics with a quantum description of the dye photophysics. I also talk about recent work on exciton transfer between dye molecules that is mediated by plasmonic nanoparticles.