  We attribute similarities in the rheology of many soft materials (foams,
emulsions, slurries, etc.) to the shared features of structural disorder and
metastability. A generic model for the mesoscopic dynamics of ``soft glassy
matter'' is introduced, with interactions represented by a mean-field noise
temperature x. We find power law fluid behavior either with (x<1) or without
(1<x<2) a yield stress. For 1<x<2, both storage and loss modulus vary with
frequency as $\omega^{x-1}$, becoming flat near a glass transition (x=1).
Values of $x\approx 1$ may result from marginal dynamics as seen in some spin
glass models.
