This talk will give an overview of some of the interesting properties and applications of surface plasmon polaritons (SPPs). These surface electron density waves are classical solutions of Maxwell's equation at the interface between a dielectric and a metal. They can be manipulated in two dimensions by fabricating nanostructures on the interface where they propagate. SPPs are extraordinarily sensitive to the nature of the interface where they propagate and can exhibit negative refraction effects. This allows the realization of unusual optical behavior such as "superlensing," "cloaking," and plasmon wave-guiding along nanoscale structures.