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.
SQLite is a small, fast, embeddable SQL database engine that supports most of SQL92, including transactions with atomic commit and rollback, subqueries, compound queries, triggers, and views. A complete database is stored in a single cross-platform disk file. The native C/C++ API is simple and easy to use. Bindings for other languages are also available.
XPA Messaging provides seamless communication between Unix programs, including X, Tcl/Tk, and generic select() loops. It provides an easy way for users to communicate with these XPA-enabled programs by executing XPA client commands from a shell. Because XPA works both at the programming level and the shell level, it is a powerful tool for unifying any environment, offering flexibility in choosing the best level at which to access XPA services. A program becomes an XPA-enabled server by defining named points of public access through which data and commands can be exchanged with other client programs (and users). Using standard TCP sockets, XPA supports both single-point and broadcast messaging to and from these servers.
tkbiff allows arbitrary commands to be executed upon mail reception. If you like programs such as xbiff and xbiff++ but wish they were more flexible, then you'll like tkbiff. Unlike other biffs, tkbiff is fully customizable. tkbiff also doesn't waste your valuable screen space with icons; instead, it shows you the mail itself. It supports UNIX, Mac, and Windows, IMAP, POP, and UNIX-style mail files, and SSL and APOP.