  Motivated by recent interest in spin triplet superconductors, we investigate
the vortex lattice structures for this class of unconventional superconductors.
We discuss how the order parameter symmetry can give rise to U(1)$\times$U(1)
symmetry in same sense as in spinor condensates, making half-quantum vortices
(HQV) topologically stable. We then calculate the vortex lattice structure of
HQV's, with particular attention on the roles of the crystalline lattice, the
Zeeman coupling, and Meissner screening, all absent in spinor condensates.
Finally, we consider how spin-orbit coupling leads to a breakdown of the
U(1)$\times$U(1) symmetry in free energy and whether the HQV lattice survives
this symmetry breaking. As examples, we examine simpler spin-triplet models
proposed in the context of NaxCoO2$\cdot$yH2O and Bechgaard salts, as well as
the better known and more complex model for Sr2RuO4.
