I visit Carlos E. Perez's Manageability blog about once a week because he occasionally posts useful list of open source Java projects along with terse yet revealing comments. I thought it might be useful to list the lists.
- Portal Servers (most recent)
- Workflow Engines
- Rule-based Engines
- Regular Expression Engines (benchmark)
- Two Fast XML Parsers
Carlos is a bit heavy on the Java cheerleading, but these gems are worth the visit.