During the last 3 months, for my Bachelor thesis, I have been doing a lot of research on unstructured peer-to-peer. I have identified and created a survey on several services that unstructured p2p can offer: membership, clustering, aggregation, random sampling, broadcast dissemination and searching.
In the paper I also reference and briefly compare current alternatives on each service.
I have thought that it may be helpful for pub/sub or other applications you build.
This is the link to the non-published paper: https://aratz.lasa.eus/file/unsserv.pdf