[hxr]

Riak.. sounds good! Is this just an implementation of Chord (http://pdos.csail.mit.edu/chord/) with a REST API?

[siculars]

similar ideas but afaik riak draws it's lineage directly from amazon's dynamo paper, http://en.wikipedia.org/wiki/Dynamo_(storage_system).

[spahl]

It does much more.

It integrates distributed MapReduce and has a sort of graph api on top of it. You can link objects together and walk the graph.