open source job scheduling system

 Quartz is a full-featured, open source job scheduling system that can
 be integrated with, or used along side virtually any J2EE or J2SE
 application - from the smallest stand-alone application to the
 largest e-commerce system. Quartz can be used to create simple or
 complex schedules for executing tens, hundreds, or even
 tens-of-thousands of jobs; jobs whose tasks are defined as standard
 Java components or EJBs. The Quartz Scheduler includes many
 enterprise-class features, such as JTA transactions and clustering.