This evening I gave the inaugural talk of the IPFS London user group, an introduction to IPFS, with some mentions of the history of the group in London (which I witnessed first hand), called "How the InterPlanetary file system became the Distributed Web". It wasn't the first time that I was talking about IPFS to a group of people but it was the first official Meetup. We had four talks in total, which was a bit crazy for a Meetup, but they all went very well. The last one, given by Ian Preston, who came all the way from Oxford to present to us, was amazing.
Peergos is essentially the complete implementation of an encrypted file system on the top of IPFS, with a permission system really granular. You can selectively give specific people (ie: specific public keys) access to some nodes of your file tree (sharing a node means sharing all its children). You can later on revoke this access and this means that the owner of the private key simply can no longer see further mutations of the node (and the subtree that it is the root of). To achieve this, the file tree has two overlays, called Cryptrees, which I had never heard of before, one along the directed links from parent to children and another one from children to parent.
There is a paper on Cryptrees, by Dominik Grolimund, Cryptree: A Folder Tree Structure for Cryptographic File Systems, which Peergos is based on.