Ghostscript is a processor for PostScript and PDF files. It can rasterize these files to a wide variety of printers, devices for screen preview, and image file formats. Since applications tend to prepare pages for printing in a high-level format such as PostScript, most Unix users with low-level bitmap printers, such as inkjets, use GhostScript as part of the printing process. In addition, Ghostscript is capable of converting PostScript files, functionality comparable to Adobe Acrobat Distiller, but on the command line. In addition, Ghostscript is used for file import and viewing by a great many other applications, including xv, ImageMagick, gimp, and xdvi. Several GUI wrappers for viewing PostScript and PDF files exist, including GSview, ghostview, gv, ggv, and kghostview. This is far from a comprehensive list.
GNU ccScript offers a class extensible threaded embedded scripting engine for use with the Common C++ GNU package. This engine is also used in Bayonne (the GNU telephony server), and in TOSI (FreeBSD and GNU/Linux PBX integration servers). This engine differs from traditional scripting systems in that it is used to script near real-time state-event systems through deterministic callback step execution rather than the linear and non-deterministic fashion of embedded script libraries such as tcl, and libguile.
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.
gfortune is a replacement for the traditional Berkeley fortune program included with the BSD games package. This implementation supports recursion down a tree of fortune files, the option to limit the number of lines output (for scripting), and other features. It fully maintains the functionality of the original. It includes the author's own archive of fortune files.
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.
imapbiff is a small perl/tk program that notifies you of new mail in an IMAP mail account. It only checks IMAP accounts, not local mail files or POP accounts. When you do not have any unread messages in your IMAP Inbox, it will display a mailbox icon with the flag lowered. When it detects new messages in your IMAP Inbox, it will beep and raise the flag. Whenever it is querying the IMAP server, a "?" is displayed to indicate that it is checking for messages.