Peermaps

Instead of fetching data from a centralized tile service, your computer fetches map data from other peers across the network. As you download map data from your peers, your computer saves that data locally so that you can share it with other people who ask for it. We’ve secured funding to improve our initial prototypes and develop new components for a fully p2p web-based map viewer to display OpenStreetMap data with rolling updates.

Source: peermaps.org