Ask HN: What are some of the best specialty websites?

By "specialty website" I mean websites maintained by one or few people that contain a wealth of expert and often opinionated information on a very specific topic. They often look like the CSS was done by a 4 year old.

Examples include:

https://www.sheldonbrown.com/harris/ - the online bible for bike repairs

http://www.reveeveille.net/ - making instruments out of plants (french)

https://piano-ology.com/ - everything about learning piano

http://www.sticksite.com/ - all about diamond willow sticks