  Hypervelocity stars (HVSs) travel with velocities so extreme that dynamical
ejection from a massive black hole is their only suggested origin. Following
our discovery of the first HVS, we have undertaken a dedicated survey for more
HVSs in the Galactic halo and present here the resulting discovery of two new
HVSs: SDSS J091301.0+305120 and SDSS J091759.5+672238, traveling with Galactic
rest-frame velocities at least +558+-12 and +638+-12 km/s, respectively.
Assuming the HVSs are B8 main sequence stars, they are at distances ~75 and ~55
kpc, respectively, and have travel times from the Galactic Center consistent
with their lifetimes. The existence of two B8 HVSs in our 1900 deg^2 survey,
combined with the Yu & Tremaine HVS rate estimates, is consistent with HVSs
drawn from a standard initial mass function but inconsistent with HVS drawn
from a truncated mass function like the one in the top-heavy Arches cluster.
The travel times of the five currently known HVSs provide no evidence for a
burst of HVSs from a major in-fall event at the Galactic Center in the last
\~160 Myr.
