MicMix (now defunct) produced a flanger in the late 1970s that had an unusual feature… the delay could be controlled by the envelope of the input signal. This made for some unusual effects!
The Dynaflanger is probably most famous from its use by Frank Zappa.
Courtesy of the original designer, here are the schematics:
http://www.ka-electronics.com/images/Dynaflanger_Tile1.JPG
http://www.ka-electronics.com/images/Dynaflanger_Tile2.JPG
http://www.ka-electronics.com/images/Dynaflanger_Tile3.JPG
http://www.ka-electronics.com/images/Dynaflanger_Tile4.JPG
Be warned, each file is about 4Mb!
He now sells THAT Corp. chips in small quantities for hobbyists so visit his main page at http://www.ka-electronics.com/
really enjoying your blog, man. keep it up!