Timo Burkard has created Herodotus: A Peer-to-Peer Web Archival System as his Master’s Thesis. The paper (PDF or PS) describes the system, which is built on top of Chord and uses the spare resources of many nodes to do the crawling and retrieval.
This is incredible! It’s awesome when you see that someone else has put together your interests (archiving and P2P) using technologies you love (the Wayback Machine and Chord). I can’t wait to play with this.