  We study the effects of short-range correlated disorder arising from chemical
dopants or local lattice distortions, on the ferromagnetism of 3d double
exchange systems. For this, we integrate out the carriers and treat the
resulting disordered spin Hamiltonian within local random phase approximation,
whose reliability is shown by direct comparison with Monte Carlo simulations.
We find large scale inhomogeneities in the charge, couplings and spin
densities. Compared with the homogeneous case, we obtain larger Curie
temperatures ($T_{C}$) and very small spin stiffnesses ($D$). As a result,
large variations of $\frac{D}{T_{C}}$ measured in manganites may be explained
by correlated disorder. This work also provides a microscopic model for
Griffiths phases in double exchange systems.
