Dave Winer has an interesting thing going with nodeStorage.
nodeStorage is an open source project that brings simple S3-based storage to applications written in JavaScript that run in the browser. [...] All web apps need to be able to store information on behalf of the user. We've had a couple of different approaches to work with that don't require an identity system -- cookies and local storage. These are good but the data is bound to a machine, not to a person. So if you went to a different machine, you'd have to start over. —What is nodeStorage?
I'm a big fan of the idea (see my older post, "We need a new kind of web storage" for more thoughts on the subject).
I haven't played around with nodeStorage, but I intend to.