I'm researching this topic, and so far I've found the following useful:
- Wikipedia: https://en.wikipedia.org/wiki/Go_variants
- Sensei's Library: https://senseis.xmp.net/?Variants
- The Go Variant Forum at Board Game Geek
- This video from 7 years ago about "crazy go" at the AGA's go congress: https://www.youtube.com/watch?v=8X4dPbyTXTU
- A 5-ish page section in New Rules for Classic Games, by R. Wayne Schmittberger
- A nice list from a website no longer online, (but available from archive.org): https://web.archive.org/web/19990427051 ... iants.html