Percona XtraDB Cluster
Percona develops Percona Server, which is Oracle's MySQL server community edition patched with a number of bug fixes, optimizations and new features, especially targeted for better statibility, monitorability and manageability. Percona Server runs on the Percona's optimized InnoDB storage engine version: XtraDB.
Percona XtraDB Cluster is cluster enabled version of Percona Server. It is based on Percona Server, which Percona has further merged with the Codership's replication API patch for MySQL (wsrep), which makes it possible to use the Galera replication plugin for clustering functionality.
Percona XtraDB Cluster went GA in April, 2012.