Official introduction.
An introduction to Durus as part of the Spyced documentation. Not that great, as pointed out in the comments.
Know How Durus 3.6: Semi-technical notes about Durus, with links to issues discussed on the mailinglist.
Moellus is a “rich and soft layer on Durus” that adds some kind of relational capability. Don’t know if anyone ever used it.
Schevo.