Mercat is a light-weight, cross platform programming language. It is garbage collected and self hosting and produces portable byte-compiled binaries that can be executed on any platform with the appropriate interpreter. Interpreters are available for Linux, DOS (32-bit) and DOS (16-bit) and the interpreter source should be easily compilable for other platforms.
GNUstep is a cross-platform, object oriented environment composed of frameworks, tools, and servers (daemons). It is very similar to the Cocoa frameworks from Apple, and tries to maintain compatibility with Cocoa wherever it is desired and possible. The frameworks provide classes for containers, distributed objects, object archiving, file management, text system, font management, image composition, WYSIWYG PostScript graphics, and more.
CircleMUD is a multi-user dungeon game system (MUD). It is a derivative of DikuMUD Gamma 0.0. A MUD (Multiple User Dimension or Multiple User Dungeon) is a computer program which allows Internet users from around the world to connect to it, create fictional characters for themselves, and then interact with other real users as well as computer-generated entities in a virtual environment.
The SWORD Project is an effort to create an ever expanding software package for research and study of God and His Word. Libraries are developed in ANSI-draft standard C++ and currently compile on Linux and in WIN32 environments. Frontends complete and currently under development include commandline tools, gtk, wxGTK, Qt, Gtk--, and WIN32 C++Builder). Addon modules include Bible texts, commentaries, lexicons, and dictionaries in a variety of languages.
XPilot is a graphical multi-player maneuvering game with less-exciting graphics, but more speed, tactics, and insults. Some people also use it for UDP network analysis. Over the past eight years of playing and development, tons of features have been added to the game, from basic weapons like shotguns and missiles to more recent ones like phasing devices, invisibility, or hyperjump.
MUMail is a Java applet designed to let you read your mail from a web page. It enables you to check your mail when there is no mail reader available, or if you don't want to change the configuration of someone else's mail reader. All you need is a Java 1.1 compliant Web browser. MUMail uses POP3 to download mail and is MIME enabled.
GNU Aspell is a spell checker designed to eventually replace Ispell. It can either be used as a library or as an independent spell checker. Its main feature is that it does a superior job of suggesting possible replacements for a misspelled word than just about any other spell checker out there for the English language. Unlike Ispell, Aspell can also easily check documents in UTF-8 without having to use a special dictionary. Aspell will also do its best to respect the current locale setting. Other advantages over Ispell include support for using multiple dictionaries at once and intelligently handling personal dictionaries when more than one Aspell process is open at once.
EO is a templates-based, ANSI-C++ compliant evolutionary computation library. It contains classes for any kind of evolutionary computation (specially genetic algorithms) you might come up to. It is component-based, so that if you don't find the class you need in it, it is very easy to subclass existing abstract or concrete class.