Valhalla DSP has released ValhallaFreqEcho, a freeware effect plug-in which combines a wide range frequency shifter with an analog style delay, for a variety of paradoxical audio effects.
Bode-style frequency shifter + analog echo emulation = skull melting chaos.
Sonic results range from subtle chorusing and double tracking, to barberpole phasing and flanging, to runaway echos spinning through your skull, to endless glissandos. Perfect for those Dr. Who sounds, dub, and all of your psychedelic needs.
ValhallaFreqEcho is available as a freeware VST plug-in for Windows and Mac (Mac AU coming).
Note: This is a pre-alpha release, so you might encounter some bugs.
More information: Valhalla DSP