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
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.
Wayback Machine - Browse through over 150 billion web pages archived from 1996 to a few months ago.
URL2PNG - Screenshots as a Service. Capture snapshots of any website, right in your app, quickly and reliably.
Perma.cc - Perma.
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.