“Main research goals of the Free Haven Project:

Anonymity: We try to meet this goal for all parties: the publishers that insert documents, the readers that retrieve documents, and the servers that store documents. We are in the process of designing and developing a free, low-latency, two-way mixnet for forward-anonymous communication.

Accountability: We consider methods for achieving accountability without sacrificing anonymity. In particular, we’re researching reputation and micropayment schemes, which allow us to limit the damage done by servers which misbehave.

Persistence: The publisher of a document — not the servers holding the document — determines its lifetime. [...]“

http://freehaven.net