BZFlag is a 3D, multiplayer, tank battle zone, capture the flag game that pits players against each other in a networked environment. It runs on Windows 95/98/NT/2000, Linux, MacOS 10.x, Irix, Solaris, and others. An OpenGL accelerator is highly recommended, but it is playable with 3D in software.
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).
e3 is a full-screen, user-friendly text editor with an interface similar to that of either WordStar, Emacs, Pico, Nedit, or vi. It's heavily optimized for size and independent of libc or any other libraries, making it useful for mini-Linux distributions and rescue disks. The assembler version supports Linux, FreeBSD, OpenBSD, NetBSD, Win9x, QNX, Atheos, BeOS, ELKS, and DOS. There is also a separately distributed version written in C which supports some other Unix versions and CygWin. It is also possible to use regular expressions by using child processes like sed. e3 has a built in arithmetic calculator.
Heroes is similar to the "Tron" and "Nibbles" games of yore, but includes many graphical improvements and new game features including 12 original soundtracks, 94 levels (in 10 different tilesets), and five gaming modes including Quest (the classical Nibbles), or Kill'em all (squish the lemmings).
Q is a powerful and extensible functional programming language based on the term rewriting calculus. When programming with Q, you specify a system of equations which the interpreter uses as rewrite rules to reduce expressions to normal form. Q is useful for scientific programming and other advanced applications, and also as a sophisticated kind of desktop calculator. The distribution includes the Q programming tools, a standard library, add-on modules for interfacing to various third-party libraries, and an Emacs mode.