Letter: C
- CCfits - A C++ interface for cfitsio
- CGAL - Computational Geometry Algorithms Library
- Canna - A Japanese character set input system.
- CastPodder - CastPodder is a Media Aggregator
- ClanLib - Cross platform C++ game library
- ClanLib06 - Version 0.6 of this Cross platform C++ game library
- Coin2 - High-level 3D visualization library
- c-ares - A library that performs asynchronous DNS operations
- c2050 - Converts bitcmyk data to Lexmark 2050 printer language
- c2070 - Converts bitcmyk data to Lexmark 2070 printer language
- cabextract - Utility for extracting cabinet (.cab) archives
- cacti - An rrd based graphing tool
- cairomm - Cairomm is the C++ API for the cairo graphics library
- cal3d - Skeletal based 3-D character animation library
- calcurse - Text-based personal organizer
- camE - Rewrite of the xawtv webcam app, which adds imlib2 support
- camstream - Set of programs to make use of your webcam
- catfish - A handy file search tool
- cbios - A third party BIOS compatible with the MSX BIOS
- ccache - C/C++ compiler cache
- ccrtp - Common C++ class framework for RTP/RTCP
- cd-discid - Utility to get CDDB discid information
- cdlabelgen - Generates frontcards and traycards for inserting in CD jewelcases
- cdo - A program for manipulating GRIB/NetCDF/SERVICE/EXTRA files
- cdogs-data - Data files for the CDogs game
- cdogs-sdl - C-Dogs is an arcade shoot-em-up
- cegui - Free library providing windowing and widgets for graphics APIs / engines
- celestia - OpenGL real-time visual space simulation
- centericq - Text mode menu- and window-driven IM
- centerim - Text mode menu- and window-driven IM
- cernlib - General purpose CERN library and associated binaries
- cfengine - A systems administration tool for networks
- cfitsio - Library for manipulating FITS data files
- cfv - A utility to test and create data verification files
- cgdb - CGDB is a curses-based interface to the GNU Debugger (GDB)
- cgoban - X board for playing go
- charis-fonts - Charis SIL fonts
- chemical-mime-data - Support for chemical/* MIME types
- chemtool - A program for 2D drawing organic molecules
- chess - 3D chess game
- childsplay - Suite of educational games for young children
- childsplay_plugins - Plugins for childsplay (educational games for young children)
- chkrootkit - Tool to locally check for signs of a rootkit
- chmlib - Library for dealing with ITSS/CHM format files
- chmsee - A Gtk+2 CHM document viewer
- chrpath - Modify rpath of compiled programs
- cjet - Converts PCL data to Canon CaPSL III printer language
- cksfv - Utility to manipulate SFV files
- clamav - End-user tools for the Clam Antivirus scanner
- clanbomber - Bomberman-like multiplayer game that uses ClanLib
- claws-mail - The extended version of Sylpheed
- claws-mail-plugins - Additional plugins for claws-mail
- clearsilver - Fast and powerful HTML templating system
- clement - An application to filter and manage E-mail traffic
- climm - Text/line based ICQ client with many features
- clips - CLIPS language for developing expert systems
- clipsmm - Clipsmm is a C++ wrapper for the CLIPS C library
- clisp - Common Lisp (ANSI CL) implementation
- cln - Class Library for Numbers
- clucene - A C++ port of Lucene
- clusterssh - Secure concurrent multi-server terminal control
- clutter - Open Source software library for creating rich graphical user interfaces
- clutter-gst - ClutterMedia interface to GStreamer
- clutter-gtk - A basic GTK clutter widget
- cmake - Cross-platform make system
- cmigemo - C interface of Ruby/Migemo Japanese incremental search tool
- cmucl - CMU Common Lisp compiler
- cobbler - Boot server configurator
- coco-coq - Coco Coq in Grostesteing's base, an AGI adventure game
- codeblocks - An open source, cross platform, free C++ IDE
- cogito - The Cogito Version Control System
- cohoba - Cohoba is a GNOME interface for Telepathy. It aims to be innovative and simple
- coldet - 3D Collision Detection Library
- colordiff - Color terminal highlighter for diff files
- comgt - Linux UMTS/GPRS command-line tool
- comix - A user-friendly, customizable image viewer
- commoncpp2 - GNU Common C++ class framework
- compat-erlang - General-purpose programming language and runtime environment
- compat-guichan05 - Compatibility libraries for older guichan versions
- compat-guile-16 - A GNU implementation of Scheme for application extensibility
- compat-libgda - Library for writing gnome database programs
- compat-libosip2 - oSIP is an implementation of SIP
- compat-wxGTK - Compatibility version of the wxWidgets GTK GUI library
- compat-wxPythonGTK2 - Compatibility version of the wxWidgets GUI toolkit for Python
- compface - Utilities for handling X-Faces
- conduit - A synchronization solution for GNOME
- cone - CONE mail reader
- conexus - C++ network and serial communication library
- conexusmm - Network and serial communication widgets for Gtkmm
- conglomerate - Extensible XML Editor
- conky - A system monitor for X
- conman - ConMan - The Console Manager
- conmux - ConMux - The Console Multiplexor
- connect-proxy - SSH Proxy command helper
- conntrack - Tool to manipulate netfilter connection tracking table
- conserver - Serial console server daemon/client
- contact-lookup-applet - Contact Lookup Applet
- contacts - Contacts addressbook
- convmv - Convert filename encodings
- cook - File construction tool
- cowbell - Music organazier
- cowsay - Configurable speaking/thinking cow
- cpan2rpm - Perl module packager
- cpanspec - RPM spec file generation utility
- cpl - ESO library for automated astronomical data-reduction tasks
- cppunit - C++ unit testing framework
- cproto - Generates function prototypes and variable declarations from C code
- crack - Password cracker
- crack-attack - Puzzle action game
- crm114 - CRM114 Bayesian Spam Detector
- cronolog - Web log rotation program for Apache
- crossfire - Server for hosting crossfire games
- crossfire-client - Client for connecting to crossfire servers
- crossfire-maps - Map files for the crossfire server
- crossvc - Graphical CVS Client
- crystal - KDE window decoration
- crystal-clear - Crystal Clear KDE Icon set
- crystal-project - Crystal Project KDE Icon set
- crystal-stacker - Falling blocks, match 3 or more of the same color crystals
- crystal-stacker-themes - Themes for the Crystal Stacker game
- csmash - 3D tabletennis game
- csound - Csound - sound synthesis language and library
- cssed - CSS editor and validator
- csync2 - A cluster synchronization tool
- ctapi-common - Common files and packaging infrastructure for CT-API modules
- ctapi-cyberjack - CT-API 1.1 driver for REINER SCT cyberjack USB chipcard reader
- ctorrent - BitTorrent Client written in C
- ctrlproxy - ctrlproxy
- cups-pdf - Extension for creating pdf-Files with CUPS
- cupsddk - CUPS Driver Development Kit
- curlftpfs - CurlFtpFS is a filesystem for accessing FTP hosts based on FUSE and libcurl
- curry - Münster Curry compiler
- cvs2cl - Generate ChangeLogs from CVS working copies
- cvs2svn - CVS to Subversion Repository Converter
- cvsgraph - CVS/RCS repository grapher
- cvsplot - Collect statistics from CVS controlled files
- cvsps - Patchset tool for CVS
- cvsutils - CVS Utilities
- cvsweb - Web interface for CVS repositories
- cycle - Calendar program for women
- cyphesis - WorldForge game server
- cyrus-imapd - A high-performance mail server with IMAP, POP3, NNTP and SIEVE support