  We compute the prepotential for gauge theories descending from ${\cal N}=4$
SYM via quiver projections and mass deformations.
  This accounts for gauge theories with product gauge groups and bifundamental
matter. The case of massive orientifold gauge theories with gauge group SO/Sp
is also described. In the case with no gravitational corrections the results
are shown to be in agreement with Seiberg-Witten analysis and previous results
in the literature.
