Beyond the Standard Model with Electron and Muon Beams

We describe the current status and future potential of precision low energy experiments using intense electron and muon beams to search for physics beyond the standard model in a manner complementary to direct searches at the Large Hadron Collider. The measurements fall under to broad categories: those that search for small deviations in precision electroweak observables that are measurable with very high precision and have correspondingly accurate calculations at the level of electroweak radiative corrections, and those observables that have very small or vanishing values within the framework of the electroweak theory but are very sensitive to new physics at the TeV scale. We review ongoing efforts and outline future initiatives that are timed to match the physics results from high integrated luminosity at the LHC.