In 2008 I wrote a bachelor thesis together with Michael Werk. The subject was P2P filesharing through a filesystem, and it's available in Danish here. Currently it needs to be further developed with respect to security and a few features, but we ended having a usable prototype. A demonstration video is also available (OGG, 1.4 MB).
To summerize the project, I'll mention the most important points:
Uses FUSE and will be cross-platform in the future
100% P2P, absolutely no servers
Full write-support
Fast for browsing and is consistent for writing
Uses its own model of P2P mixing Kademlia and Gossiping
