  Three dimensional topologically massive gravity (TMG) with a negative
cosmological constant -\ell^{-2} and positive Newton constant G admits an AdS_3
vacuum solution for any value of the graviton mass \mu. These are all known to
be perturbatively unstable except at the recently explored chiral point
\mu\ell=1. However we show herein that for every value of \mu\ell< 3 there are
two other (potentially stable) vacuum solutions given by SL(2,R)x
U(1)-invariant warped AdS_3 geometries, with a timelike or spacelike U(1)
isometry.
  Critical behavior occurs at \mu\ell=3, where the warping transitions from a
stretching to a squashing, and there are a pair of warped solutions with a null
U(1) isometry. For \mu\ell>3, there are known warped black hole solutions which
are asymptotic to warped AdS_3. We show that these black holes are discrete
quotients of warped AdS_3 just as BTZ black holes are discrete quotients of
ordinary AdS_3. Moreover new solutions of this type, relevant to any theory
with warped AdS_3 solutions, are exhibited. Finally we note that the black hole
thermodynamics is consistent with the hypothesis that, for \mu\ell>3, the
warped AdS_3 ground state of TMG is holographically dual to a 2D boundary CFT
with central charges c_R={15(\mu\ell)^2+81\over G\mu((\mu\ell)^2+27)} and
c_L={12 \mu\ell^2\over G((\mu\ell)^2+27)}.
