skalibs is a set of general-purpose, low-level C libraries, all in the public domain. It can replace or hide the standard C library to some extent. It is designed to allow building of small static binaries. It is used in building all skarnet.org software, including execline and s6.
Micro Tetris is based on the 1989 International Obfuscated C Code Contest Best Game entry. It is a very small implementation, with extreme similarity to the BSD Tetris implementation. So it is very suitable for small embedded systems with only serial or SSH console access. The code uses no curses or other heavy libraries, only ANSI escape sequences and the Unix "stty" command to setup and restore the display.
execline is a very light, non-interactive scripting language, which is similar to a shell. Simple shell scripts can be easily rewritten in the execline language, improving performance and memory usage. execline was designed for use in embedded systems, but works on most Unix flavors.
Finit is a small SysV init replacement with process supervision similar to that of daemontools and runit. Its focus is on small and embedded GNU/Linux systems, although it is fully functional on standard server and desktop installations. Finit is fast because it starts services in parallel; it then supervises and automatically restarts them if they fail. This can be extended upon with custom callbacks for all services, hooks into the boot process, or plugins to extend the functionality and adapt Finit to your needs. Finit is not only fast, it’s arguably one of the easiest to get started with. A complete system can be booted with one simple configuration file.
spectrwm is a minimalistic tiling window manager that tries to stay out of the way so that valuable screen real estate can be used for much more important stuff. It has sane defaults and does not require one to learn a language to do any configuration. It was written by hackers for hackers and it strives to be small, compact, and fast.