PalmsNorth.com

It's a bit Russian but it's pretty simple to follow. The formatting could use some work but it should definitely help you trying to identify some of your unknown cacti.

http://www.samaracactus.ru/holland1.htm

Thanks for sharing.

I wish I had that cactus collection over 450 cacti. Looks like it was done back in 2006 I wonder how much bigger they are now...

I notice some of the name's he used have been superseded by other names but at least it can put you on the right track.