Stumbled across this effect while looking for a completely different schematic. It's a low cost chorus designed by Merlin Blencowe (here's his schematic for reference), using a PT2399. It generates deep modulation and a very thick warble (here's a sound clip).
This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.