  We give a review of some recent work on the construction and classification
of $p$-brane solutions in maximal supergravity theories in all dimensions $4\le
D\le 11$. These solutions include isotropic elementary and solitonic
$p$-branes, dyonic $p$-branes, and multi-scalar $p$-branes. These latter two
categories include massless strings and black holes as special cases. For all
the solutions, we analyse their residual unbroken supersymmetry by means of an
explicit construction of the eigenvalues of the \bog matrix, defined as the
anticommutator of the conserved supercharges.
