  We study systematically various extensions of the Poincar\'e superalgebra.
The most general structure starting from a set of spinorial supercharges
$Q_\alpha$ is a free Lie superalgebra that we discuss in detail. We explain how
this universal extension of the Poincar\'e superalgebra gives rise to many
other algebras as quotients, some of which have appeared previously in various
places in the literature. In particular, we show how some quotients can be very
neatly related to Borcherds superalgebras. The ideas put forward also offer
some new angles on exotic branes and extended symmetry structures in M-theory.
