Screenshot Machine - Screenshot machine is an online website capturing service. Creates a screenshot or thumbnail of any online web page in couple of seconds for free.
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
URL2PNG - Screenshots as a Service. Capture snapshots of any website, right in your app, quickly and reliably.
Wayback Machine - Browse through over 150 billion web pages archived from 1996 to a few months ago.
ApiFlash - ApiFlash is a powerful serverless screenshot API built with Chromium and AWS Lambda. It can easily scale to millions of screenshots per day and has an ever growing number of satisfied big clients.
Perma.cc - Perma.