Metallic nanoparticles embedded in dielectrics permit enhanced capture of light at specific wavelengths through excitation of plasmons, i.e. the quanta of coherent and collective oscillations of large concentrations of nearly free electrons. In order to maximize the potential of such enhanced absorption in useful tasks, such as the generation of carriers in photocatalysis and semiconductors, it is important to be able to predict and design plasmonic nanocomposites with desired wavelength-dependent optical response. Recently, a mixing approach formulated by Garcia and coworkers [Phys. Rev. B, 75, 045439 (2007)] has been successfully applied to model the experimentally measured broadband optical absorption for ternary nanocomposites containing alloys or mixtures of two metals (from Ag, Au or Cu) in SiO2 dielectric. In this work we present the broadband optical behavior of important optical coating dielectrics Si3N4 and SiO2 and photocatalyst TiO2 containing various configuration of nanoparticles of Al, Au, Ag, or Cu. The spectral behavior of various combinations of the metallic species in the dielectrics was optimized to show its use as an anti-reflecting coating on Si or strong multiple plasmonic absorption peaks. The applications of such nanocomposite materials in solar energy harvesting and spectral sensing are also presented and discussed.