RavenDB is a 2nd generation NoSQL database of the Document DBs type. It has many advanced features, and it is very good at what it does. RavenDB is written in .NET but can be accessed from any programming language.
With RavenDB you can get any application requiring a data store up and running very fast due to some advanced concepts it is built on. It is meant to be used by the heaviest of modern applications, even at web-scale. And it is always evolving to becoming faster, more flexible and more developer friendly.