Bound electromagnetic waves existing in a form of collective oscillations of surface charges in thin metallic films and nanoparticles are now widely known as surface plasmons. The most prominent property of surface plasmons is that they are able to concentrate electromagnetic energy to deep subwavelength volumes, thereby greatly increasing the local density of photonic states. This in turn gives rise to a number of possible amplification mechanisms for various spectroscopic and light-matter interaction phenomena including Raman scattering, fluorescence, local refractive index sensitivity and light harvesting. In this lecture we will discuss recent progress along these lines.