C library for creating IP packets

https://github.com/libnet/libnet

Library and transmitter that implements ICE-19

https://nice.freedesktop.org

Library and transmitter that implements ICE-19

http://nice.freedesktop.org/

Library and transmitter that implements ICE-19

https://nice.freedesktop.org

C library, API for communicating with Creative and Dell audio players

http://libnjb.sourceforge.net/

Library for desktop notifications

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

Astronomical Calculation Library

https://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/

Open Fingerprint Architecture Library

http://code.google.com/p/musicip-libofa/

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

Wrapping library to the System Tools Backends

Library for camera RAW files decoding

https://libopenraw.freedesktop.org/

Freedesktop synchronization framework

http://www.opensync.org/

Library for handling OpenType fonts

https://www.nongnu.org/m17n/

Portable OTR Messaging Library and toolkit

https://otr.cypherpunks.ca/

Library providing routines for paper size management

https://packages.qa.debian.org/libp/libpaper.html

Ubiquitous network traffic capture library

https://www.tcpdump.org/

libpcap wrapper library

https://netdude.sourceforge.net/

PCI configuration space I/O made easy

https://mj.ucw.cz/sw/pciutils/

Generic PCI access library

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

Next evolution of the Gedit plugins engine

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

Library to handle Apple Property List format

https://www.libimobiledevice.org

Library for transforming bitmaps into vector graphics

http://potrace.sourceforge.net

Library that provides automatic proxy configuration management

https://libproxy.github.io/libproxy/

Weak aliases for pthread functions

https://xcb.freedesktop.org/

Library for generating random passwords and quality checking

https://github.com/libpwquality/libpwquality

Multi-purpose desktop calculator (backend library)

http://qalculate.github.io/

C library for encoding data in a QR Code symbol

https://github.com/fukuchi/libqrencode

Embedded lua scripts for libquvi and utility scripts

http://quvi.sourceforge.net/

Embedded lua scripts for libquvi and utility scripts

http://quvi.sourceforge.net/

Cross-platform library for parsing flash media stream URLs

http://quvi.sourceforge.net/

Easy access to RESTful web services

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

Library for parsing and rendering SVG vector-graphic files

https://live.gnome.org/LibRsvg

RTMP stream library

https://rtmpdump.mplayerhq.hu/

Secret Rabbit Code: a Sample Rate Converter for audio

http://www.mega-nerd.com/SRC/

Library to access the secret service API

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

Extension widgets for GTK+

http://releases.chipx86.com/libsexy/libsexy/

Connect and transmit data to an Icecast media streaming server

https://icecast.org/ https://gitlab.xiph.org/xiph/icecast-libshout

Commodore SID-chip emulator library to play SID music files

Callback Framework for C++

http://libsigc.sourceforge.net/

Callback Framework for C++

http://libsigc.sourceforge.net/

Handling page faults in user mode

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

Routines for rapid alpha-numeric terminal applications development

https://www.jedsoft.org/slang/

Reading and writing files containing sampled sound (like WAV or AIFF)

http://www.mega-nerd.com/libsndfile/

Personal social data server.

SOAP (Simple Object Access Protocol) implementation in C

https://libsoup.org/