  In this paper we extend the Cosmological Constant Seesaw treatment of
hep-th/0602112 to String/M-Theory where the cosmological constant is finite. We
discuss how transitions between different $\lambda$, one of Planckian vacuum
energy, can give rise to a large $M_{Pl}^4$ denominator in the Cosmological
Constant Seesaw relation discussed by Banks, Motl and Carroll. We apply these
ideas to 2d/3d String/M-Theory and show how the existence of a large N dual
fermionic theory makes the demonstration of a transition between different
$\lambda$ relatively straight forward. We also consider 2d/3d Heterotic
String/M-Theory cosmology, a theory for which the large N dual is unknown. The
minisuperspace associated to these models is 26/27 dimensional for the SO(24)
theory and 10/11 dimensional for the $SO(8) \times E_8$ theory and consists of
the $T$ fields as well as the dilaton and metric. 2d Heterotic String Quantum
Cosmology is similar to critical string dynamics except for the inclusion of
the 2d gauge fields. These 2d gauge fields have an important effect on the
vacuum energy and on transitions between different $\lambda$ through the
effects of Wilson lines. Finally we discuss the extension to existing higher
dimensional string cosmologies possessing large N duals.
