  We study the long-term evolution of massive black hole binaries (MBHBs) at
the centers of galaxies using detailed full three-body scattering experiments.
Stars, drawn from a distribution unbound to the binary, are ejected by the
gravitational slingshot. We quantify the effect of secondary slingshots --
stars returning on small impact parameter orbits to have a second super-elastic
scattering with the MBHB -- on binary separation. Even in the absence of
two-body relaxation or gas dynamical processes, very unequal mass binaries of
mass M=10^7 solar masses can shrink to the gravitational wave emission regime
in less than a Hubble time, and are therefore a target for the planned Laser
Interferometer Space Antenna (LISA). Three-body interactions create a
subpopulation of hypervelocity stars on nearly radial, corotating orbits, with
a spatial distribution that is initially highly flattened in the inspiral plane
of the MBHB, but becomes more isotropic with decreasing binary separation. The
mass ejected is ~0.7 times the binary reduced mass, and most of the stars are
ejected in an initial burst lasting much less than a bulge crossing time.
