  We present a multi-frequency, multi-epoch catalog of extragalactic sources.
The catalog is based on 150, 220, and 280 GHz observations carried out in 2008,
2009, and 2010 using the Millimeter Bolometric Array Camera on the Atacama
Cosmology Telescope. We also present and release 280 GHz maps from 2008 and
2010. The catalog contains 483 sources found in a sky area of ${\sim}600$
square degrees. It was obtained by cross-matching sources found in 11
sub-catalogs, one for each season and frequency band. We also include co-added
data from ${\sim}150$ and ${\sim}160$ square degrees using two and three years
of overlapping observations. We divide the sources into two populations,
synchrotron and dusty emitters, based on their spectral behavior in the 150-280
GHz frequency range. We find 284 synchrotron sources and 183 dusty source
candidates. Our cross-matching with catalogs from radio to X-ray results in 251
synchrotron sources (88%) and 92 dusty sources (51%) with counterparts and
suggests that 91 dusty candidates are not in existing catalogs. We study the
variability and number counts of each population. In the case of synchrotron
sources, we find year-to-year variability, with a mean value around 35%. As
expected, we find no evidence of dusty source variability. Our number counts
generally agree with previous measurements and models, except for dusty sources
at 280 GHz, where some models overestimate our results.
