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.
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.
Werc is a minimalistic RESTful Web application framework and content management system. It follows the Unix "tool philosophy" and it is designed to be fast, simple, convenient, and easily extensible. It handles both small and big sites and has a flexible system for user and group permissions. All data is stored in plain text files that can be easily manipulated with standard tools, without using any databases or other external dependencies. Existing applications include a blogging engine with RSS/Atom feeds, a wiki system that can easily integrate pre-existing documents (can be enabled for any directory tree), and others.
m9u is a music server, similar to mpd or xmms2. It sits in the background, waiting for commands to be delivered via a 9p file system. m9u embraces the Unix philosophy of doing one thing well. As such, it does not try to catalog or otherwise organize music, but aims for the more humble goal of simply playing it. A side effect of this approach is that m9u is trivially extensible to domains aside from music (for example, an image slideshow).
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.