I will present an overview of recent efforts to calculate the
interactions among hadrons using lattice QCD. After outlining the
techniques that are used to extract scattering parameters, I will detail
the latest calculations of meson-meson scattering, baryon-baryon 
scattering and multi-meson systems obtained by the NPLQCD collaboration.
Estimates of the computational resources required to achieve precision
results in the baryon sector will be presented.