GObject collection library

https://wiki.gnome.org/Projects/Libgee

The GGZ Gaming Zone - Base Library

http://www.ggzgamingzone.org/

Common GL api library used by Mesa based ports

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

Program that keeps passwords and other secrets

Support library for gnome cups admistration

http://www.gnome.org/

Common error values for all GnuPG components

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

Universal digital camera control library

http://www.gphoto.org/proj/libgphoto2/

Extensible i/o abstraction for dealing with structured file formats

http://www.gnumeric.org

GObject based library for rendering XPS documents

https://wiki.gnome.org/action/show/Projects/libgxps

Implementation of the IETF Calendaring and Scheduling protocols

https://github.com/libical

Character set conversion library

https://www.gnu.org/software/libiconv/

ID3 tags library (part of MAD project)

http://mad.sourceforge.net/

Internationalized Domain Names command line tool

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

C library that supports plugin printer driver for Ghostscript

http://www.linuxprinting.org/ijs/

Library to communicate with Apple iOS devices

http://www.libimobiledevice.org

ODBC 3.x driver manager, for universal data source access

http://www.iodbc.org/

Library for Evation's Irman infrared receiver

https://libirman.sourceforge.io/

Standalone client/server 9P library

https://libs.suckless.org/deprecated/libixp/

Codec for karaoke and text encapsulation for Ogg

https://wiki.xiph.org/index.php/OggKate

Library to make X.509 certificates

https://www.gnupg.org/aegypten2/

Lightweight Open Sound Control implementation

http://liblo.sourceforge.net/

Easy to use C/C++ seam carving library

http://liblqr.wikidot.com/

System independent dlopen wrapper

https://www.gnu.org/software/libtool/

Libmad library (part of MAD project)

https://www.underbit.com/products/mad/

A library encapsulating malsync

http://jasonday.home.att.net/code/libmal/

Multi-cipher cryptographic library (used in PHP)

http://mcrypt.sourceforge.net/

C library for accessing a memcache cluster

https://people.FreeBSD.org/~seanc/libmemcache/

Set of utilities to benchmark productivity of system calls

http://hub.opensolaris.org/bin/view/Project+libmicro/

MikMod Sound Library

http://mikmod.sourceforge.net/

Multiple-image Network Graphics (MNG) reference library

https://www.libmng.com/

ModPlug mod-like music shared libraries

http://modplug-xmms.sourceforge.net/

Abstraction around libmpdclient

http://gmpc.wikia.com/

Free library for decoding mpeg-2 and mpeg-1 video streams

http://libmpeg2.sourceforge.net/

Library for Microsoft compression formats

https://www.cabextract.org.uk/libmspack/

MusicBrainz client library for audio metadata lookup

http://musicbrainz.org/

MusicBrainz client library for audio metadata lookup

http://musicbrainz.org/

C library for creating IP packets

https://sourceforge.net/projects/libnet-dev/

Library and transmitter that implements ICE-19

https://nice.freedesktop.org

Library and transmitter that implements ICE-19

http://nice.freedesktop.org/

Library for desktop notifications

https://gitlab.gnome.org/GNOME/libnotify

Astronomical Calculation Library

http://libnova.sourceforge.net/

Library that implement Microsoft's NTLM authentication

https://www.nongnu.org/libntlm/

C library implementing the OAuth Core standard

http://liboauth.sourceforge.net/

Replacement Objective-C runtime supporting modern Objective-C features

https://github.com/gnustep/libobjc2/

OpenSource implementation of the OFX (Open Financial eXchange)

http://libofx.sourceforge.net/

Ogg bitstream library

https://www.xiph.org/ogg/

Library of optimized inner loops

https://liboil.freedesktop.org/wiki/

Old X library

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

Library for handling OpenType fonts

http://www.nongnu.org/m17n/

Portable OTR Messaging Library and toolkit

https://otr.cypherpunks.ca/