Hey Drew, how confortable do you feel with modular software environments? If you don't mind some DIY type stuff check out Plogue Bidule and AudioMulch.
PlogueBidule hosts VSTs inside, and itself can be a VST inside another host, so you can load Plogue Bidule into your DAW, and then load your other VST FX inside Bidule to connect and route to each other in some fucked up ways, including creating feedback loops. So, you could for example take a filter plugin, route it into a delay module, then feedback the output of the delay back into the filter, while modulating filter cutoff. Obviously you'll need to take care not to let things get too out of hand when playing with feedback
I don't believe AudioMulch can be used inside a DAW, it's a standalone program, but it too has some rather interesting built-in modules and you can load stuff in there to help you mangle audio in any which way you please. It's got a built-in sample player, so you can load your audio into it, pass it through some contracptions and off you go.