The Fink project wants to bring the full world of Unix Open Source software to Darwin and Mac OS X. It modifies Unix software so that it compiles and runs on Mac OS X and makes it available for download as a coherent distribution. Fink uses Debian tools like dpkg and apt-get to provide powerful binary package management. You can choose whether you want to download precompiled binary packages or build everything from source.
fli4l is a single-floppy Linux-based ISDN/DSL/ethernet-router. It features configuration with some simple ASCII-files, several possible connection-flavors (in/out/callback, and raw IP/PPP), channel bundling (an extra channel can be added through a Windows/Unix-client), configuration of multiple networks, least-cost routing, automatic choice of provider, display/calculation of connection times and costs, and a Windows/Unix client to control dial/hangup, monitor traffic and monitor incoming calls on ISDN (see screenshot).
FLTK (pronounced "fulltick") is a cross-platform C++ GUI toolkit for UNIX/Linux (X11), Microsoft Windows, and Mac OS X. It provides modern GUI functionality without the bloat, and supports 3D graphics via OpenGL and its built-in GLUT emulation. FLTK is designed to be small and modular enough to be statically linked, and also works fine as a shared library. It also includes an excellent UI builder called FLUID that can be used to create applications in minutes.
Freeciv is a multiuser reimplementation for Unix/X of the famous Microprose game of Civilization. By default, the game is an improved Civ II, but this can be customized; modpacks for near-100% compatibility with Civ I and Civ II are included. Multiuser gameplay is real-time: in each turn, all human players move concurrently. The game is designed to remain fairly playable even on poor network connections. Freeciv can also be played on standalone machines, and its AI players are a good challenge for beginners. The source code comes with the server, two X clients, and non-X clients for MS Windows and Amiga. Freeciv is released under the GNU General Public License. It is maintained by an international team of coders and enthusiasts, and is easily one of the most fun and addictive network games out there.
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.
gEDA is a suite of electronic design automation (EDA) tools. Currently, the project offers a mature suite of free software applications for electronics design, including schematic capture, attribute management, bill of materials (BOM) generation, netlisting into over 20 netlist formats, analog and digital simulation, and printed circuit board (PCB) layout.