KnoBot [UPDATE: the link is often broken. the knobot page on Sourceforge is always up (thanks Zbigniew)]- An agent for decentralised knowledge exchange :KnoBot combines semantic web technology with a P2P design to build a trust based decentralised system for information selection and discovery.
I should check it better but looks a lot like what I want to do for my PhD.
On KnoBot news I found a similar and interesting project: the Matrix Public Network project.
Both ot the project have running code, so we can try them out.