Mathomatic is a portable, general-purpose computer algebra system (CAS) that can solve, differentiate, simplify, combine, and compare algebraic equations, perform standard, complex number, modular, and polynomial arithmetic, etc. It does some calculus and is very easy to compile/install, learn, and use. The symbolic math application with a simple command-line interface is designed to be a colorful algebra calculator that is reliable, responsive, and convenient to use. The symbolic math library is lightweight and easy to include in other software, due to being written entirely in C with no additional dependencies.
audiopreview is a command-line tool that plays previews of many audio file types (Ogg, MP3, etc.), video file types (AVI, MPEG, Real, etc.), and Internet streams. It can also be used as a regular command-line media file player (i.e. play the files entirely like yauap or mpc123 would).
vitunes is a curses-based music player and playlist manager whose goals are a minimalistic appearance, strong vi-like bindings, and quick playlist creation/management. It does not strive to be a full-blown media player, but rather a full-blown media indexer and playlist manager. It uses MPlayer to support a wide range of media formats. It also makes use of TagLib for metadata extraction from many common formats.
id321 is a command line ID3 tag manipulation tool. It supports reading and writing of ID3 tags of the following versions: ID3v1, ID3v1.1, ID3v1.2, ID3v1.3, enhanced tag, ID3v2.2, ID3v2.3, and ID3v2.4. The utility can force standards of ID3 tags in order to fix existing non-standard tags.
The klish is a framework for implementing Cisco-like command-line interfaces on Unix systems. It is configurable through XML files. "Klish" stands for "Kommand Line Interface SHell". The klish is a fork of clish-0.7.3. The original clish was developed by Graeme McKerrell. The klish adds some new features, but is compatible (as much as possible) with clish's XML configuration files.
excat is a simple tool that auto-detectd (potentially nested) compressed file formats and decompresses any combination of them using libarchive, thus unifying zcat, bzcat, lzcat, xzcat, etc. in a single (static, if you need it) binary. It may act as a drop-in replacement for any *cat.