I archive quite a bit of the content that I access on the Web.
This page contains links to some of the archived content that cannot be accessed anymore.
I suggest that if there is something you like on the web you archive it.

Artists

I created pixiv_down to download all the works that artists I follow upload on pixiv, though sometimes there are other sources as well.
This is a list of artists I've confirmed to have removed their account:

Piapro

Sudoku

I enjoy trying to complete a Sudoku each day.
I used to visit the New York Times website, but have since purchased a book containing various types of Sudokus.

The following (seemingly) don't keep a public and freely accessible archive.
Please note that these are designed to be printed.