  Graphene exhibits quantum Hall ferromagnetism in which an approximate SU(4)
symmetry involving spin and valley degrees of freedom is spontaneously broken.
We construct a set of integer and fractional quantum Hall states that break the
SU(4) spin/valley symmetry, and study their neutral and charged excitations.
Several properties of these ferromagnets can be evaluated analytically in the
SU(4) symmetric limit, including the full collective mode spectrum at integer
fillings. By constructing explicit wave functions we show that the lowest
energy skyrmion states carry charge $\pm 1$ for {\em any} integer filling, and
that skyrmions are the lowest energy charged excitations for graphene Landau
level index $|n| \le 3$. We also show that the skyrmion lattice states which
occur near integer filling factors support four gapless collective mode
branches in the presence of full SU(4) symmetry. Comparisons are made with the
more familiar SU(2) quantum Hall ferromagnets studied previously.
