  We propose a novel way to manipulate the transport properties of massless
Dirac fermions by using velocity barriers, defining the region in which the
Fermi velocity, $v_{F}$, has a value that differs from the one in the
surrounding background. The idea is based on the fact that when waves travel
accross different media, there are boundary conditions that must be satisfied,
giving rise to Snell's-like laws. We find that the transmission through a
velocity barrier is highly anisotropic, and that perfect transmission always
occurs at normal incidence. When $v_{F}$ in the barrier is larger that the
velocity outside the barrier, we find that a critical transmission angle
exists, a Brewster-like angle for massless Dirac electrons.
