  Effective Field Theory (EFT) provides a powerful framework to exploit a
separation of scales in order to perform systematically improvable,
model-independent calculations. We apply this method to strongly interacting
quantum systems with short-range interactions and large scattering length. Such
systems display remarkable universal properties which include a geometric
spectrum of shallow three-body states called "Efimov states" and log-periodic
dependence of scattering observables on the scattering length. We review the
EFT for large scattering length and some of its applications in the physics of
cold atoms and nuclear physics. In particular, we discuss the possibility of an
infrared limit cycle in QCD and the extension of the EFT to halo nuclei.
