I think the Java standard library docs fall in this category. It's always been one of my favorite part of working with the language. (I guess the library desig

I think the Java standard library docs fall in this category. It's always been one of my favorite part of working with the language. (I guess the library design is controversial, or rather, it is now... Collections are looking rather outdated just to cite the obvious. But as for the documentation, it's still killer.)