  Conformally invariant sigma models in $D=2n$ dimensions with target
non-compact O(2n,1) groups are studied. It is shown that despite the
non-compact nature of the O(2n,1) groups, the classical action and Hamiltonian
are positive definite. Instanton field configurations are found to correspond
geometrically to conformal ``stereographic'' mappings of $R^{2n}$ into the
Euclidean signature $AdS_{2n}$ spaces. Zaikov's relationship between Self Dual
$p$-branes and Chern-Simons $p'$-branes, provided $p=p'+1$ and the embedding
$D=p+1$-dimensional manifold is Euclidean, is elaborated further. Branes
actions can be obtained also from a Moyal deformation quantization of
Generalized Yang Mills Theories. Using this procedure, we show how four
dimensional SU(N) YM theories contain Chern-Simons membranes and hadronic bags
in the large $N$ limit. Since Chern-Simons $p'$-branes have an underlying
infinite dimensional algebra containing $W_{1+\infty}$, as shown by Zaikov, we
discuss the importance that $W$ geometry should have in the final formulation
of $M$ theory.
