  The electronic structure of single crystals Na$_{0.6}$CoO$_2$, which are
closely related to the superconducting Na$_{0.3}$CoO$_2$.$y$H$_2$O ($T_c \sim
5K$), is studied by angle-resolved photoelectron spectroscopy. While the
measured Fermi surface is found to be consistent with the prediction of a local
density band theory, the energy dispersion is highly renormalized, with an
anisotropy along the two principle axes ($\Gamma$-$K$, $\Gamma$-$M$). Our ARPES
result also indicates that an extended flat band is formed slightly above $E_F$
along $\Gamma$-$K$. In addition, an unusual band splitting is observed in the
vicinity of the Fermi surface along the $\Gamma$-$M$ direction, which differs
from the predicted bilayer splitting.
