  We present an updated catalog of 1300 objects in the field of M31, including
670 likely star clusters of various types. Archival images were inspected to
confirm cluster classifications where possible, but most of the classifications
were based on spectra taken of ~1000 objects with the Hectospec fiber
positioner and spectrograph on the 6.5m MMT. The spectra and images of young
clusters are analyzed in detail in this paper. Ages, reddenings and masses of
140 young clusters are derived by comparing the observed spectra and photometry
with model spectra. We find these to have masses as great as 10^5 with a median
of 10^4 M_sun, and a median age of 0.25 Gyr. Thus these clusters are similar in
mass to the LMC young massive clusters, and are in between Milky Way open
clusters and the globulars of M31 and the Milky Way. Most of the M31 young
clusters have the low concentration typical of Milky Way open clusters, and we
expect that most of these will be disrupted in the next Gyr, but a few have
high concentrations and will likely survive longer. The spatial distribution of
the young clusters is well correlated with the star-forming regions as mapped
out by mid-IR emission. A kinematic analysis likewise confirms the spatial
association of the young clusters with the young disk in M31.
