GNU's Ubiquitous Intelligent Language for Extension, a library implementation of the Scheme language plus various convenient facilities. Designed to be linked into programs to make them extensible.
Powerful (Turing-equivalent) implementation of traditional Unix macro-expansion program, designed as preprocessor to more stubborn languages. Ugly, but fairly standard, available on most platforms.
MIX Development Kit, emulates MIX, MIXAL; with compiler, virtual machine, GUI, Guile interpreter, Emacs mode, Elisp program to run programs in Emacs window.
GNU (Free Software Foundation) program to create, destroy, resize and copy PC disk partitions. It currently supports ext2 and FAT (FAT16 and FAT32) filesystems, Linux swap devices, and MS-DOS disk labels. GNU/Linux or on boot disk, open source.
Portable Threads: portable POSIX/ANSI-C library for Unix gives non-preemptive priority-based scheduling for multithreading in programs. All threads run in same address space, each has its own program counter, run time stack, signal mask, errno variabl...