Amber-X

Amber-X is a free granular synthesis application for OS X, based upon Amber by Matt McCabe and Jennifer Bernard.

Amber-X takes in WAVs and AIFFs and breaks them into tiny grains, or sub-sounds, then reassembles them in interesting ways defined by the user.
Amber-X allows for control over grain size and density either linearly or with graphing functions, grain generation type, and grain envelopes, among other parameters.