Here's a description of what CouchDB is from their website:
CouchDB is written in Erlang, but can be easily accessed from any environment that provides means to make HTTP requests. There are a multitude of third-party client libraries that make this even easier for a variety of programming languages and environments.
I haven't installed or tested it out, but it looks like a really cool idea for a small efficient database design. I always find it interesting to hear about some of these cool "new" projects that look at everyday problems in new and different ways.