An overview will be presented of a variety of efficient computational techniques for evaluation of scattering of electromagnetic and acoustic waves by inhomogeneous media. In particular I will mention perturbative methods for scattering and eigenvalue problems, accurate integral scattering solvers and new high-frequency integral approaches. The applications to be presented include volumetric microscopy via optical coherence, oceanic scattering, and evaluation of radar cross-sections for remote sensing, communications, etc.