Tudu Lists is a J2EE application for managing todo lists. It's based on Spring 2.5, JPA/Hibernate and AJAX (using the DWR framework). It's a simple yet effective project management tool, and it is also often used as a sample Spring application.
Plug-in task list client for Jboss Jbpm, based on the Wicket framework. Allows you to include customized BPM functionality inside your web application.