  This is a review of some beautiful matrix models related to the moduli space
of Riemann surfaces as well as to noncritical c=1 string theory at self-dual
radius. These include the Penner model and the W-infinity model, which have
different origins but are equivalent to each other. In the final section, which
is new material, it is shown that these models are also equivalent to a
Liouville matrix model. We speculate that this might be interpreted in terms of
N D-instantons of the c=1 string.
