  This is the first release of optical spectroscopic data of low-redshift Type
Ia supernovae (SNe Ia) by the Carnegie Supernova Project including 604
previously unpublished spectra of 93 SNe Ia. The observations cover a range of
phases from 12 days before to over 150 days after the time of B-band maximum
light. With the addition of 228 near-maximum spectra from the literature we
study the diversity among SNe Ia in a quantitative manner. For that purpose,
spectroscopic parameters are employed such as expansion velocities from
spectral line blueshifts, and pseudo-equivalent widths (pW). The values of
those parameters at maximum light are obtained for 78 objects, thus providing a
characterization of SNe Ia that may help to improve our understanding of the
properties of the exploding systems and the thermonuclear flame propagation.
Two objects, namely SNe 2005M and 2006is, stand out from the sample by showing
peculiar Si II and S II velocities but otherwise standard velocities for the
rest of the ions. We further study the correlations between spectroscopic and
photometric parameters such as light-curve decline rate and color. In agreement
with previous studies, we find that the pW of Si II absorption features are
very good indicators of light-curve decline rate. Furthermore, we demonstrate
that parameters such as pW2(SiII4130) and pW6(SiII5972) provide precise
calibrations of the peak B-band luminosity with dispersions of ~0.15 mag. In
the search for a secondary parameter in the calibration of peak luminosity for
SNe Ia, we find a ~2--3-sigma correlation between B-band Hubble residuals and
the velocity at maximum light of S II and Si II lines.
