One possibility opened up by all this processing power we have now is the use of complex multi-effects configurations built by the user. You can build all kinds of crazy sound processing machinery using systems designed for this purpose like Max or Pure Data, or systems designed to be synthesizers with audio input options, such as Reaktor or the Nord Modular.
It's nice to see more options in this area, though I could see how difficult it would be to troubleshoot an increasingly configuration like this, especially in a live setting.
Something I've enjoyed doing from time to time for experimental purposes is wiring up a crazy, complex signal chain all through my studio, creating feedback loops along the lines of the things I've seen Eno set up. You have to include compressors or limiters in the loop so the setup doesn't just feedback on itself into an ever-increasing racket. Often this just creates a hum, or a throbbing oscillation, but sometimes it can be useful.
I've done this, too. I started with the two open reel "Frippertronics" delay approach very early on. It was fun to do, but the real work came in having to decide on playback what small portion of it might be salvageable. Sounds generated from internal mixer/effects-related feedback is interesting, too, but your noise floor can ramp up pretty quickly. One of pioneers in the mixer feedback area was David Myers, who went by the name Arcane Device. I thought he created some great industrial soundscapes with just a mixer, an occasional effect and feedback.