X11 Extension library

http://www.freedesktop.org/Software/xlibs

X Fixes extension library

http://www.freedesktop.org/Software/xlibs

X font library

https://www.freedesktop.org/wiki/Software/xlibs/

The Xfontcache library

http://www.x.org/

X Input extension library

http://www.freedesktop.org/Software/xlibs

X11 Xinerama library

http://www.freedesktop.org/Software/xlibs

X Miscellaneous Utilities libraries

https://www.freedesktop.org/wiki/Software/xlibs/

X print library

http://www.freedesktop.org/Software/xorg

X Pixmap library

http://www.freedesktop.org/Software/xlibs

X Resize and Rotate extension library

http://www.freedesktop.org/Software/xlibs

X Render extension library

http://www.freedesktop.org/Software/xlibs

X Resource usage library

http://www.freedesktop.org/Software/xlibs

X Toolkit library

https://www.freedesktop.org/wiki/Software/xlibs/

Network API translation layer for X applications and libraries

http://www.freedesktop.org/Software/xlibs

X Test extension

http://www.freedesktop.org/Software/xorg

X Video Extension library

http://www.freedesktop.org/Software/xlibs

X Video Extension Motion Compensation library

https://www.freedesktop.org/wiki/Software/xlibs/

X DGA Extension

http://www.freedesktop.org/Software/xorg

X XF86-Misc Extension

http://www.freedesktop.org/Software/xorg

X Vidmode Extension

http://www.freedesktop.org/Software/xorg

Portable audio output library

https://www.xiph.org/ao/

Library to create and read several streaming archive formats

https://libarchive.org/

Library for high-performance 2D graphics

http://www.levien.com/libart/

Atomic operations access library

https://github.com/ivmai/libatomic_ops

Standard C resolver library

https://www.isc.org/software/libbind

Libburnia library to read/write optical discs

https://dev.lovelyhq.com/libburnia/web/wikis/home

Library to access data on a CDDB server

http://libcddb.sourceforge.net/

Compact Disc Input and Control Library

http://www.gnu.org/software/libcdio/

Read audio from the CDROM directly as data

http://www.gnu.org/software/libcdio/

Unit test framework for C

http://check.sourceforge.net/

Tool to check shared library links

http://svn.idaemons.org/cgi-bin/viewvc.cgi/trunk/?root=libchk

Grand Central Dispatch API support library

http://libdispatch.macosforge.org/

DMX extension library

http://www.freedesktop.org/Software/xorg

Simple interface to low level networking routines

https://github.com/5u623l20/libdnet/

Standard library for Window Maker dock apps

http://solfertje.student.utwente.nl/~dalroi/libdockapp/

Userspace interface to kernel Direct Rendering Module services

https://dri.freedesktop.org/

Portable abstraction library for DVD decryption

https://www.videolan.org/developers/libdvdcss.html

Videolan version of the libdvdnav project

https://www.videolan.org/developers/libdvdnav.html

MPlayer version of the libdvdread project

https://www.videolan.org/developers/libdvdnav.html

Full-featured and high-performance event loop library

http://software.schmorp.de/pkg/libev.html

API for executing callback functions on events or timeouts

https://libevent.org/

Library for inspecting program's backtrace

http://www.gnu.org/software/libc/manual/html_node/Backtraces.html

Library to read digital camera file meta-data

https://libexif.github.io/

Foreign Function Interface

https://sourceware.org/libffi/

The fontenc Library

https://www.x.org/

Library routines for working with Flashpix images

https://www.i3a.org/

General purpose crypto library based on code used in GnuPG

https://www.gnupg.org/software/libgcrypt/index.html

Support library for gnome cups admistration

http://www.gnome.org/

Programming reference for print/libgnomeprint

http://www.gnome.org/projects/gnome-print/

Common error values for all GnuPG components

https://www.gnupg.org/software/libgpg-error/