  Over the past few decades, a consensus picture has emerged in which roughly a
quarter of the universe consists of dark matter. I begin with a review of the
observational evidence for the existence of dark matter: rotation curves of
galaxies, gravitational lensing measurements, hot gas in clusters, galaxy
formation, primordial nucleosynthesis and cosmic microwave background
observations. Then I discuss a number of anomalous signals in a variety of data
sets that may point to discovery, though all of them are controversial. The
annual modulation in the DAMA detector and/or the gamma-ray excess seen in the
Fermi Gamma Ray Space Telescope from the Galactic Center could be due to WIMPs;
a 3.5 keV X-ray line from multiple sources could be due to sterile neutrinos;
or the 511 keV line in INTEGRAL data could be due to MeV dark matter. All of
these would require further confirmation in other experiments or data sets to
be proven correct. In addition, a new line of research on dark stars is
presented, which suggests that the first stars to exist in the universe were
powered by dark matter heating rather than by fusion: the observational
possibility of discovering dark matter in this way is discussed.
