Earlier this week, Archive-It (the subscription-based collection development service from the Internet Archive) implemented Memento support for their collections, including the newly established "all" collection. This is a follow-on from the recent Internet Archive upgrade of their Memento support in the Wayback Machine. Prior to Archive-It's support of Memento, their collections were included in the Memento aggregator by proxy. While dozens of archives are included in the aggregator via proxies, native Memento support is faster and more functional.
Here is an HTTP snippet using an archived PDF of a NASA report from an earlier post about NTRS.
There are now five major, public web archives with native Memento support: Archive-It, Internet Archive's Wayback Machine, the British Library's UK Web Archive, the UK National Archives, and the Archive.is on-demand service. Thanks to all the usual suspects at LANL and IA, but special thanks go to Ilya Kremer for making this happen.