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:

AAlib is a portable ASCII art graphics library. Internally, it works like a graphics display, but the output is rendered into gorgeous platform independent ASCII graphics.

This is a highway trip planning program, similar to programs like Rand McNally's "TripMaker." It allows you to plan road trips between two or more locations, using various interchangeable map files (or databases).

Horizon is an Electronic Design Automation (EDA) tool for circuit board design. It manages the full design flow from schematic entry to gerber export. The main differentiator from KiCAD is a different (more sane) part library design. It is quite new software in 2018 so may have rough edges but is already very capable.

Perl-style regexps have many useful features that the standard POSIX ones don't; this is basically the same as grep but with the different regexp syntax.

This web service allows one to browse a rich set of molecular structures provided by the package chemical-structures-data, and eventually have them translated to other open formats, thanks to openbabel.