Spectral information enhances our knowledge of astronomy, chemistry, metallurgy, and meteorology, and it contributes to applications in photonics, communications and medical instrumentation. Different specialties may use one of many spectral selection methods, as each has particular advantages. Some applications may require high transmission and a broad field of view for 2-D imaging, while others need narrow spectral resolution or a broad tuning range. Size, cost, aperture, stability, and spectral purity are other filter considerations to be prioritized. Additionally, many applications require some means of spectral tuning.This article describes, in terms of applications potential, a wide variety of filter options, from simple ruled gratings and glass prisms to more complex acousto-optical tunable filters, crystal Bragg gratings, holographic filters, interference filters, Fabry-Perot filters and polarization interference filters.