ChBg is for changing desktop backgrounds in a given period. It can render images with 10 modes (such as tiled, centered, scaled, etc.). It uses Imlib1, Imlib2, or gdk_pixbuf for loading images, so it supports many image formats. ChBg has a windowed setup program, is able to load setup files, can be used as slideshow picture previewer in its own window or as a desktop background, and can be used as screensaver or as an xscreensaver hack. It has a dialog for fast previewing of pictures and very usable thumbnail previews.
cthumb allows you to create Web albums of digital pictures with thumbnails, captions, and several different views of the collection, including (optionally) several languages and resolutions. An album is composed of a series of pages, each composed of a collection of pictures. You can have several annotations per picture, and can customize almost everything in the way the albums look on the screen.
ctrlxmms is a small Perl script designed to increase the useability of XMMS. With it, you can use most of the common GUI functions of XMMS from the CLI. You also have a few handy commands which are not available from the GUI. Together with lirc and a remote (eg. Anir Multimedia Magic), this is a wonderful tool.
CYCAS is a 2D+3D CAD package for drafting and design in high quality and for creating 3D presentations and technical illustrations easily. Some of its features include an easy-to-handle user interface, special architectural elements and functions, a WYSIWYG display, printing, plotting, import and export filters, photorealistic rendering with POV-Ray, documentation and tutorials, example drawings, and an extendable 2D/3D symbols library.
DarkIce is a live audio streamer. It records audio from an audio interface (e.g. a sound card), encodes it, and sends it to a streaming server. DarkIce can record from OSS audio devices, ALSA audio devices, Solaris audio interfaces, and Jack sources. DarkIce can encode into MP3, MP2, Ogg Vorbis, and AAC formats, and can send the encoded stream to ShoutCast, IceCast 1.3.x and 2.x, and the Darwin Streaming Server.
dave's cd player (dcd) is a simple command-line CD player. It plays CDs, loops (sequences of) tracks, plays tracks at random, and so on. Its a full featured, but simple-to-use CD player. It supports libmusicbrainz (musicbrainz.org) for CD information if desired, yet remains one of the leanest CD players out there.
DigitalDJ is an SQL-based MP3-player frontend designed for people who want to create an MP3 version of their CD collection. It is designed to work with the Grip ripping/encoding application (but can be used separately). When Grip encodes MP3 files, it will place all of the song information into an SQL database. DigitalDJ can then use this information to create playlists based on a number of criteria.