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.
A small library that provides a powerful and container-less Dependency-Injection mechanism, via AspectJ and Groovy. If you are tired of reams of XML configuration files, managing complex factories and containers, this non-API solution may appeal to you.