Android Unix Epoch Converter is a tool that converts Unix timestamps to and from human readable time.

JGraph is a free, mature, and robust Java Graphing framework that fully complies with Swing design principles. It contains all the graph visualization and interaction functionality you might expect in a graph library, including multiple views, layering, zoom, drag and drop, undo, automatic expanding and collapsing, routing, and layouts. You can create stunning workflow editors, call graphs, CAD tools, network diagrams, database visualization tools, and more. It can also be deployed on the server-side with a large range of image exporting functionality. It is fully documented and commercially supported....

FBReaderJ is an e-book reader for the Android platform. It is a clone of the FBReader book reader written in Java.

FBReaderJ supports several e-book formats: oeb, epub, fb2. In future releases the list will be extended to support the same formats as the original FBReader. Direct reading from zip, tar and gzip archives is supported....

JBoss Cache is a product designed to cache frequently accessed Java objects in order to dramatically improve the performance of applications. By eliminating unnecessary database access, JBoss Cache decreases network traffic and increases the scalability of applications....

YaCy is a P2P search engine for the WWW including a crawler and HTTP proxy,

The Minecraft Mod API. see also CraftBukkit the impl.
Bukkit is an up-and-coming Minecraft Server mod that will completely change how running and modifying a Minecraft server is done - making managing and creating servers easier and providing more flexibility. Learning from the mistakes made by other mods, Bukkit aims to be different and fill the void left by them: built from the ground up we've focused on performance, ease-of-use, extreme customisability and better communication between the Team and, you, our users. The overall design of Bukkit has been inspired by other mods and our experience as Minecraft players just like yourselves, giving us a unique perspective and advantage going into the creation of the Bukkit Project....

Apache Rave is a new web and social mashup engine. It will provide an out-of-the-box as well as an extensible lightweight Java platform to host, serve and aggregate (Open)Social Gadgets and services through a highly customizable and Web 2.0 friendly front-end. Rave is targeted as an engine for internet and intranet portals and as a building block to provide context-aware personalization and collaboration features for multi-site/multi-channel (mobile) oriented and content driven websites and (social) network oriented services and platforms. For the OpenSocial container and services the (Java) Apache Shindig has been be integrated. Apache Rave also transparently supports W3C Widgets using Apache Wookie....

JNode is a simple to use & install Java operating system for personal use.

It runs on modern devices.

Any java application will run on it, fast & secure!

JNode is open source and uses the LGPL license.

...but may come over in a while. GPL license is probably slightly different.

Commons Configuration provides a generic configuration interface which enables a Java application to read configuration data from a variety of sources, e.g. properties files, XML files, Windows INI files, etc. Commons Configuration provides typed access to single, and multi-valued configuration parameters....