CouchDB is a (relatively) new database option for development that focuses on documents, rather than generic relational systems like most databases do. I think the concept is appealing and support for things like automatic versioning and distributed processing and storage could mean a lot fewer headaches that trying to get a custom system going yourself. Also interesting is the JSON storage format, which would make this ideal to use in many asynchronous web applications as the data returned can be used straight away on the browser.
I haven't had any cause to use this system yet but I'll be sure to write a review when I do. Anyone else taken this for a spin?