Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Wayback Machine - Browse through over 150 billion web pages archived from 1996 to a few months ago.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
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
Better Uptime - We call you when your website goes down
Time Travel - Prebook rides for Uber