Redis is one of a few up-and-coming persistent, non-relational data stores. Although similar to memcached in API, it goes further than memcachedb by extending the command set in addition to persisting the data.

The other big name I'm hearing is Tokyo Cabinet, but I haven't had a chance to try it yet.

The current beta release of Redis includes a Python client library. I had good reference implementations to work from in django.contrib.sessions.backends and some free time, so I put together a Redis session backend. It's being used on this site, and the source is available here. I'd package it, but my current thinking is that I'm simply not OCD enough to package things correctly.

Obviously, this is nice as a replacement for memcache sessions since memcached has that little feature of being a cache rather than a store.

P.S. Why didn't anyone point out that I can't spell "disappoint"? Sigh... I've fixed the article, but the URL is forever.