Wayback Machine - Browse through over 150 billion web pages archived from 1996 to a few months ago.
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
FreezePage - FreezePage is a free service for taking online snapshots of web pages.
blit - Automated, scheduled, screenshots to your inbox.
oldweb.today - Time travel across the world wide web using old browsers
Resurrect Pages - Dead pages, broken links, the scourge of the internet.