  We completely describe all semi-stable torsion free sheaves of degree zero on
nodal cubic curves using the technique of Fourier-Mukai transforms. The
Fourier-Mukai images of such sheaves are torsion sheaves of finite length,
which we compute explicitly. We show how to obtain an SL(2,Z)-action (up to
shifts) on the bounded derived category of coherent sheaves on any Weierstass
cubic.
