Started working on a pseudonymous, secure and decentralized messaging system. Features:
Everybody is identified by the hash of his public key. Exchanging this identifier over a secure channel (in real life) or via trusted third parties ("If you need help with this, contact my good friend Bob (rsa-sha1:38484848)") is all that is needed to have secure communication. The local client will map those identifiers to (local) human readable nick names.
No peers communicate directly without prior negotiation via other peers. This has a lot of advantages: It is easy to implement downstream bandwith throttling; Peers can hide their participation in this network to the world (most other p2p networks will widely distribute your IP adress.) and even stay completely anonymous by the use of mix chains; and it makes it possible to implement DoS/Spam-defences which are impossible to implement in a network where everybody can send to everbody else without prior negotiation.
Message routing uses xor metric. This scales (a limited search horizon is acceptable in a file sharing network but not in a messaging system) and eleminates the use of central servers.