  Accretion disk reflection spectra, including broad iron emission lines, bear
the imprints of the strong Doppler shifts and gravitational red-shifts close to
black holes. The extremity of these shifts depends on the proximity of the
innermost stable circular orbit to the black hole, and that orbit is determined
by the black hole spin parameter. Modeling relativistic spectral features,
then, gives a means of estimating black hole spin. We report on the results of
fits made to archival X-ray spectra of stellar-mass black holes and black hole
candidates, selected for strong disk reflection features. Following recent
work, these spectra were fit with reflection models and disk continuum emission
models (where required) in which black hole spin is a free parameter. Although
our results must be regarded as preliminary, we find evidence for a broad range
of black hole spin parameters in our sample. The black holes with the most
relativistic radio jets are found to have high spin parameters, though jets are
observed in a black hole with a low spin parameter. For those sources with
constrained binary system parameters, we examine the distribution of spin
parameters versus black hole mass, binary mass ratio, and orbital period. We
discuss the results within the context of black hole creation events,
relativistic jet production, and efforts to probe the innermost relativistic
regime around black holes.
