CJDNS (fc00::/8) is a friend-to-friend meshnet with end-to-end encryption that carries IPv6 traffic. Its aim is to replace the internet, perhaps preferably at the link-level. It uses MPLS-like routing locally together with a DHT and floodfill for global routing. There is no built-in support for routing through other darknets, but it is possible to setup with a bit of bash-fu (e.g. onioncat or socat).
It is not built with anonymity as a goal. It just *accidentally* have a lot of the features we seek.
Yggdrasil can probably scale better, although it have currently not yet grown as large. It is somewhat more anon-friendly.
A partial map of CJDNS.