distributed.net is a loosely knit group of computer users from all of the world that is taking up challenges requiring lots of computing power (most notably the RC5, DES, and OGR cracking contests). It is simple to participate in the challenges by downloading and running their client software (which uses idle CPU time to complete its tasks).
Spin Chat is a completely Java based Chat application, both server and client. It has been originally developed on Linux and runs excellent on it. It features vast customization possibilities, multi-channels, built-in spam control, graphical administration tools, I18N, channel logging, ignoring, emotes, etc.
Cfengine is a tool for setting up and maintaining BSD and System-5-like operating system optionally attached to a TCP/IP network. You can think of cfengine as a very high level language, much higher level than Perl or shell: a single statement can result in many hundreds of operations being performed on multiple hosts. Cfengine is good at performing a lot of common system administration tasks, and allows you to build on its strengths with your own scripts.
BlueJ is an interactive Java development environment. It provides a unique user interface that presents a graphical display of the application classes and their relationships, and it lets users interactively create objects of any class. Once objects have been created, users can interact with them directly. This interaction mechanism allows for much greater testing and experimentation than in conventional environments. BlueJ is suited for teaching and learning OO and Java.
ClanLib is a cross-platform game SDK currently supporting Windows and Linux. It provides easy-to-use interfaces for 2D graphics, input, sound, resources, networking, GUI, OpenGL, and more. The goal is to provide a game SDK that does all the dirty work that all modern games need to implement anyway, thus making the game developer concentrate on the gameplay instead of reinventing the wheel over and over again.
DXSpider is a Ham Radio program that connects to other similar programs by radio or the internet and provides a real-time information service to Ham Radio operators rather like IRC. It is designed to become a complete replacement for the original DOS implementation written by Dick Newell AK1A.
Quat is a program for generation of 3d fractal objects. These objects are Julia sets using quaternions. Features include calculation of usual images and stereo pair images for real 3d views, a user-specified true color palette for flexible coloring, 5 iteration formulas, and intersection planes to view the interior of the three-dimensional fractal. A text mode version for batch calculation is also available.
JExpress is a Java installer builder and auto-updater. It gives you your choice of a standalone installer, including both native and cross platform installers and updaters for Windows, Mac OS X, Linux, and Solaris, or a Java Web Start one-click install. You create your installer quickly with your choice of a simple wizard or a powerful advanced interface, both included. You can bundle the exact JVM you want with your installer. The auto-updater gives you a continuous revenue stream after the sale. Your software is always up-to-date, so your customers have fewer problems. You also get all the features you expect in a top end installer. Your Java application becomes a native program just like any other. On Windows it's an EXE, on Mac OS X an app bundle, etc. If you need something really special, you can customize your installer by adding simple Java classes. You can even get a source license at a reasonable price.