Via freshmeat, Clustered JDBC:
Clustered JDBC is to databases what RAID is for disks. C-JDBC provides transparent database clustering (partitioning, replication, etc.) to any Java application through JDBC. It works with any Java application without code modification and with any datase engine. C-JDBC has been successfully tested with Tomcat, JBoss, JOnAS, MySQL, PostgreSQL, HSQL, SAP DB, Oracle, and more.