The Interactive Way To Go
The Interactive Way To Go is a Go tutorial for players who have never played Go before. It defines such players as 50 kyu, and takes them, through explanation of rules, and basic concepts, up to 30k, usually known as beginner level.
It starts from the basic rules, then introduces concepts as the ladder, the net, and eyes.
It is usually recommended as a way to learn for people interested in Go, because of its simple teaching style and use of java applets to allow people to experiment.
There are many translations available of this website due to its popularity. You can choose it at the bottom left of the window.
The author of the site and the program is Hiroki Mori.
Modern remake: https://way-to-go.gitlab.io/
Spiritweaver This was one of my starting points when I learned about go. It's one of my personal favorites.