Berkeley DB (libdb) is a programmatic toolkit that provides embedded database support for both traditional and client/server applications. It includes b+tree, queue, extended linear hashing, fixed, and variable-length record access methods, transactions, locking, logging, shared memory caching, database recovery, and replication for highly available systems. DB supports C, C++, C#, Java, PHP, and Perl APIs. It supports key-value pair (NoSQL), SQL, and Java Object formatted data. It is available for a wide variety of Unix platforms as well as QNX, Android, Mac OS X, and several varieties of Windows.
BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
f/Calc is a utility to calculate lens formulae for photographers so you can focus on the artistic bits rather than on the mathematics behind it all. f/Calc can do "f" number arithmetic, and can calculate depth of field, hyperfocal distance, the field of view of a lens, the angle of view of a lens, magnification, and how the focal length of the lens on the camera changes the way the spot metering function works. In addition to the Unix/Linux Tcl/Tk version, there are native Windows, Palm OS, and Macintosh versions as well.