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.
Frodo is a free, portable C64 emulator. It focuses on the exact reproduction of graphical effects possible on the C64, and comes in three "flavors" (Frodo, Frodo PC, and Frodo SC) with increasingly higher quality of emulation, but at the cost of higher processing power requirements. Frodo has been ported to a number of systems, including handheld computers. The Unix version can use either SDL, X11, or SVGAlib to display the graphics.
getmail is intended as a simple, secure, and reliable replacement for fetchmail. It retrieves email (either all messages, or only unread messages) from one or more POP3, SPDS, or IMAP4 servers (with or without SSL) for one or more email accounts, and reliably delivers into qmail-style Maildirs, mboxrd files, or through external MDAs (command deliveries) specified on a per-account basis. getmail also has excellent support for domain (multidrop) mailboxes, including delivering messages to different users or destinations based on the envelope recipient address.
KVEC is a command line tool that allows you to convert raster graphics to vector graphics. KVEC is designed for 32 bit operating systems and runs on Win32, OS/2, HP-UX, NEXTSTEP, Linux, IRIX, AIX 4.x, Macintosh and BeOS. Docs are available in English and German. The shareware version is available for 30 day trial.