  We describe how the D-brane spectra of the various ten-dimensional string
theories can be related to general properties of the open-closed duality,
encoded in the $S$ and $P$ matrices of the conformal field theory. We also
complete the classification and the description of non-BPS branes in these
string theories, elucidating their non-Abelian structures and the nature of the
corresponding super-Higgs mechanisms. We find that the type 0 theories and
their orientifolds have two types of uncharged branes, distinguished by their
couplings to the closed string tachyon. We also find that the 0A orientifold
has the unusual feature of having charged and uncharged branes with identical
world-volume dimensions. We conclude with some comments on fractional branes,
elucidating their role in connection with the boundary states of $D_{odd}$
SU(2) WZW models.
