http://www.hadoop.org/
The Apache Hadoop project develops open-source software for reliable, scalable, distributed computing, including:

• Hadoop Core, our flagship sub-project, provides a distributed filesystem (HDFS) and support for the MapReduce distributed computing metaphor.
• HBase builds on Hadoop Core to provide a scalable, distributed database.
• Pig is a high-level data-flow language and execution framework for parallel computation. It is built on top of Hadoop Core.
• ZooKeeper is a highly available and reliable coordination system. Distributed applications use ZooKeeper to store and mediate updates for critical shared state.
• Hive is a data warehouse infrastructure built on Hadoop Core that provides data summarization, adhoc querying and analysis of datasets.