Apache Lenya is an Open Source Java/XML Content Management System and comes with revision control, site management, scheduling, search, WYSIWYG editors, and workflow.

oVirt is a web based virtual machine management application. It builds on libvirt, Ruby, Rails, and collectd to provide a VM management application able to scale from a handful of machines to an entire data center. It integrates with FreeIPA to provide Kerberos single signon, and uses ISCSI for VM storage....

MarkdownJ is the pure Java port of Markdown (a text-to-html conversion tool written by John Gruber.)

Roma is an Open Source initiative to make Java application development easy. The approach is totally DDD: let's think to the domain of your application and Roma will make the rest: persistence (database), presentation (HTML + Ajax), logging, user management, sessions, workflow, scheduler, etc....

OrientDB is a deeply scalable Document-Graph DBMS with the flexibility of the Document databases and the power to manage links of the Graph databases. It can work in schema-less mode, schema-full or a mix of both. Supports advanced features such as ACID Transactions, Fast Indexes, Native and SQL queries. It imports and exports documents in JSON. Graphs of hundreads of linked documents can be retrieved all in memory in few milliseconds without executing costly JOIN such as the Relational DBMSs do....

Marauroa is Arianne's Multiplayer Online Engine Server, that you can use to build you own online games using Marauroa as a Content Management system.

Marauroa is completly written in Java using a multithreaded server architecture with a TCP oriented network protocol, a mySQL based persistence engine and a flexible game system based on open systems totally expandible and modifiable by developers and that is able to run scripts on Python for the game's rules....

Apache Harmony is the Java SE project of the Apache Software Foundation.

The aim of the project is to produce a large and healthy community of those interested in runtime platforms tasked with creation of:

- a compatible, independent implementation of Java SE under the Apache License v2...

The IcedTea project provides a harness to build the source code from http://openjdk.java.net using Free Software build tools and provides replacements for the binary plugs with code from the GNU Classpath project.

JBoss AOP is a 100% Pure Java aspected oriented framework usuable in any programming environment or tightly integrated with our application server. Aspects allow you to more easily modularize your code base when regular object oriented programming just doesn't fit the bill. It can provide a cleaner separation from application logic and system code. It provides a great way to expose integration points into your software. Combined with JDK 1.5 Annotations, it also is a great way to expand the Java language in a clean pluggable way rather than using annotations solely for code generation....

ImageJ is a public domain Java image processing program inspired by NIH Image for the Macintosh. It runs, either as an online applet or as a downloadable application, on any computer with a Java 1.4 or later virtual machine. Downloadable distributions are available for Windows, Mac OS, Mac OS X and Linux....