If you don't want to purchase above screencast to learn about an next generation, document-oriented database. You can view some CouchDB talks (source CouchDB Wiki):
2008 August 27th: CouchDB to BBC web developers (Slides, Notes)
2008 June 27th: CouchDB, Erlang eXchange (Slides)
2008 March 17th: CouchDB from cover to cover (Slides)
Another database I'm tracking is Scalaris: a young, peer-to-peer, distributed, academic awards storage engine.
The concept of Scalaris is very simple: Scalaris is a transactional data store for online services based on the peer-to-peer principle. It provides self-management and scalability by replicating services among peers. Without system interruption it scales from a few PCs to thousands of servers. Servers can be added or removed on the fly without any service downtime.
Scalable Wikipedia with Erlang, Google Scalability Conference, Seattle, June 2008 (slides)
Building a transactional distributed data store with Erlang, Erlang eXchange, London, June 2008 (slides)