Pekwm is a window manager that once up on a time was based on the aewm++ window manager, but it has evolved enough that it no longer resembles aewm++ at all. It has a much expanded feature-set, including window grouping (similar to ion, pwm, or fluxbox), autoproperties, xinerama, keygrabber that supports keychains, and much more.

Open Babel is a chemical toolbox designed to speak the many languages of chemical data. It allows one to search, convert, analyze, or store data from molecular modeling, chemistry, solid-state materials, biochemistry, or related areas. Features include:

picocom was designed to serve as a simple, manual, modem configuration, testing, and debugging tool. It has also served (quite well) as a low-tech "terminal-window" to allow operator intervention in PPP connection scripts (something like the ms-windows "open terminal window before / after dialing" feature). It could also prove useful in many other similar tasks. It is ideal for embedded systems since its memory footprint is minimal.

spectrwm is a small dynamic tiling window manager for X11.

The xkb plugin shows you the current keyboard layout and allows you to switch to different defined layouts.

GNU dc is a reverse-polish desk calculator which supports unlimited precision arithmetic. It also allows you to define and call macros.