Cassandra 2.0 dropped today from the Apache Software Foundation.
If you don’t know Cassandra, check out the Getting Started guide.
Or visit Planet Cassandra that describes Cassandra this way:
Apache Cassandra is a massively scalable open source NoSQL database. Cassandra is perfect for managing large amounts of structured, semi-structured, and unstructured data across multiple data centers and the cloud. Cassandra delivers linear scalability and performance across many commodity servers with no single point of failure, and provides a powerful dynamic data model designed for maximum flexibility and fast response times.
Enjoy!