  We present 348 X-ray emitting stars identified from correlating the Extended
Chandra Multiwavelength Project (ChaMP), a serendipitous wide-area X-ray
survey, with the Sloan Digital Sky Survey (SDSS). We use morphological
star/galaxy separation, an SDSS quasar catalog, an optical color-magnitude cut,
and X-ray data quality tests to create our catalog, the ChaMP Extended Stellar
Survey (ChESS), from a sample of 2121 matched ChaMP/SDSS sources. Our cuts
retain 92% of the spectroscopically confirmed stars while excluding 99.6% of
the 684 spectoscopically confirmed extragalactic sources. Fewer than 3% of the
sources in our final catalog are previously identified stellar X-ray emitters;
we expect ~10% of the catalog is composed by giants, and identify seven giant
stars and three cataclysmic variables. We derive distances, X-ray and
bolometric luminosities for these stars, revealing that this catalog fills the
gap between the nearby stars identified by the ROSAT All-Sky Survey and the
more distant stars detected in deep Chandra and XMM-Newton surveys. For 36
newly identified X-ray emitting M stars we calculate L_(Halpha)/L_(bol).
L_(H\alpha)/L_(bol) and L_(X)/L_(bol) are linearly related below L_(X)/L_(bol)
~ 3 x 10^(-4), while L_(Halpha)/L_(bol) appears to turn over at larger
L_(X)/L_(bol) values. Stars with reliable SDSS photometry have an ~0.1 mag blue
excess in (u-g), likely due to increased chromospheric continuum emission.
Photometric metallicity estimates suggest the sample is split between the young
and old disk populations of the Galaxy; the lowest activity sources belong to
the old disk population, a clear signature of the decay of magnetic activity
with age. Future papers will present analyses of source variability and
comparisons of this catalog to models of stellar activity in the Galactic disk.
