ndc Plugs has released Cycle Shifter, an open source VST effect plug-in for Windows and OS X.
Cycle Shifter reads in a single cycle of input audio, then (at the end of the cycle) outputs it on top of the current input audio, repeating the process ad infinitum. It works best on long, sustained sounds like strings and pads, sounding like a strange kind of noisy/gentle distortion. You won't hear much effect on drums because they generally have such a high frequency content.
