Genius is an arbitrary precision integer and multiple precision floating point calculator. It includes its own programming language similar in some aspects to C, bc, or Pascal. It can deal with rational numbers and complex numbers. It has matrix support as well. It uses the gmp library so it is very fast for calculations of large numbers. It has a command line and a GNOME interface. The GNOME interface supports plotting functions and 3D surfaces.
Cfengine is a tool for setting up and maintaining BSD and System-5-like operating system optionally attached to a TCP/IP network. You can think of cfengine as a very high level language, much higher level than Perl or shell: a single statement can result in many hundreds of operations being performed on multiple hosts. Cfengine is good at performing a lot of common system administration tasks, and allows you to build on its strengths with your own scripts.
pdnsd is a Proxy DNS server for Linux and FreeBSD that is designed to cope with unreacheable nameservers (e.g. because the dial-in link is not up) in a graceful manner to prevent DNS-dependent applications like Netscape from hanging. It has a permanent disk cache (i.e. the cache contents are saved in a file on exit) and supports parallel query and a wide variety of link uptests. It also has the ability to serve some types of locally defined records.
Shrimp is a visual workflow to the RenderMan shader creation, written on top of the FLTK2 library and using OpenGL for scene display. It will let you connect blocks of functions in a visual fashion much like an electronic CAD package, and it will create a preview from the connected shaders (surface, displacement, light, etc). Once satisfied, you can export the resulting shaders and use them in your 3D scenes using any RenderMan compliant engine, such as Aqsis, 3Delight, or PRMan.
Eukleides is a computer language devoted to elementary plane geometry. It aims to be a fairly comprehensive system to create geometric figures, either static or dynamic. It can handle geometric types of data like points, vectors, lines, circles, or conics. A Eukleides script usually consists of a declarative part where objects are defined and a descriptive part where objects are drawn. Nonetheless, Eukleides is also a full featured programming language, providing conditional and iterative structures, user defined functions, modules, etc. The Eukleides distribution provides two distinct interpreters: "eukleides" and "euktopst". The former interpreter produces Encapsulated PostScript (EPS). The latter produces PSTricks macros, allowing Eukleides to be used with LaTeX.
E-MailRelay is a simple SMTP store-and-forward mail transport agent (MTA). It runs as an SMTP server, storing incoming e-mail in a local spool directory, and then forwarding the stored messages to a downstream SMTP server on request. It can also run as a proxy server, forwarding (and optionally pre-processing) incoming e-mail as soon as it is received. It does not do any message routing other than to a local postmaster. Because of its simplicity E-MailRelay is extremely easy to configure, typically requiring only the address of the downstream SMTP server to be put on the commandline.