See http://www.cubrid.org/cluster. CUBRID Cluster is an open source clustered DBMS for high scalability including global schema, distributed partition and load balancing features. It is a spin-off project from CUBRID project and supported by NHN.
OpenJCS (Job Control System) is a batch scheduling and control system for use on Unix systems which uses load balancing, dependency control, scheduling, runbooks, queueing and resource allocation subsystems for unmatched scalability and flexibility.
The Plugin Framework for Java is a distributed Plugin framework. It will enable users to write distributed application by just writing simple Plugins. It will come with Plugin clustering, central plugin registry and load balancing.
Sequoia is a database clustering middleware offering load balancing and transparent failover. Databases are replicated over multiple nodes and Sequoia balances the queries between them. Sequoia supports online maintenance and recovery operations.