We consider configurations of Neveu-Schwarz fivebranes, Dirichlet fourbranes
and an orientifold sixplane in type IIA string theory. Upon lifting the
configuration to M-theory and proposing a description of how to include the
effects of the orientifold sixplane we derive the curves describing the Coulomb
branch of N=2 gauge theories with orthogonal and symplectic gauge groups,
product gauge groups of the form SU(k_1)...SU(k_i) x SO(N) and
SU(k_1)...SU(k_i) x Sp(N). We also propose new curves describing theories with
unitary gauge groups and matter in the symmetric or antisymmetric
representation.Comment: 29 pages (harvmac b-mode), 2 figure