Implicit BPM is a platform for integrating business processes into existing core applications as if they were a whole system. It uses a novel concept, namely Workflow Weaving, based on non-intrusive techniques, which achieves this kind of integration transparently.
Rapidlogix is an open source application performance management tool optimized for distributed production environments. It allows to increase time-to-market of performance improvements and prevent performance regression
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.