ar5iv tracks the arXiv collection with a one month lag. Exactly as to signal that this is not the "official" arXiv rendering. It is also a showcase predating the arXiv /html/ route, but largely using the same technology. Nowadays maintained by the same people (hi!)

There used to be another showcase, called arxiv-vanity. They captured what happened pretty well with their farewell post on their homepage:

https://www.arxiv-vanity.com/