Archive.md - archive.is allows you to create a copy of a webpage that will always be up even if the original link is down
Resurrect Pages - Dead pages, broken links, the scourge of the internet.
Wayback Machine - Browse through over 150 billion web pages archived from 1996 to a few months ago.
oldweb.today - Time travel across the world wide web using old browsers
Perma.cc - Perma.
Archive-It - Archive-It is a free to use web archiving service designed for the libraries and archives.