Full-featured and high-performance event loop library

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

Linux Event Device library

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

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/

Application library for the Xfce desktop environment

https://www.xfce.org/

Video encoding library

http://fame.sourceforge.net/

Foreign Function Interface

https://sourceware.org/libffi/

C++ library for building platform-independent programs

https://lib.filezilla-project.org/

The fontenc Library

https://www.x.org/

Library routines for working with Flashpix images

https://www.i3a.org/

Library (using libusb) to talk to FTDI chips

http://www.intra2net.com/de/produkte/opensource/ftdi/

General purpose crypto library based on code used in GnuPG

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

Provides uniform access to different kinds of data sources

https://www.gnome-db.org/

Provides Berkeley DB backend for the libgda5 library

https://www.gnome-db.org/

Provides Java DB Connector backend for the libgda5 library

https://www.gnome-db.org/

Provides ldap access for the libgda5 library

https://www.gnome-db.org/

Provides mdb backend for the libgda5 library

https://www.gnome-db.org/

Provides mysql backend for the libgda5 library

https://www.gnome-db.org/

Provides postgresql access for the libgda5 library

https://www.gnome-db.org/

The libgda 5 ui library

https://www.gnome-db.org/

GLib based implimentation of the GData protocol

http://live.gnome.org/libgdata

GDI+ API for System.Windows.Forms in Mono

https://www.mono-project.com/docs/gui/libgdiplus/

GObject collection library

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

GObject based library for handling and rendering epub documents

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

The GGZ Gaming Zone - Base Library

http://www.ggzgamingzone.org/

Gigasampler file loader library

http://www.linuxsampler.org/

Portable, pure C implementation of the Git core

https://libgit2.github.com/

Glib wrapper library around the libgit2 git access library

https://git.gnome.org/browse/libgit2-glib

Library providing su and sudo functionality

http://www.gnu.org/non-gnu/gksu/

GNOME glade library

Collection of video game music emulators

https://bitbucket.org/mpyne/game-music-emu

Libraries for GNOME, a GNU desktop environment

http://www.gnome.org/

Small library intended for internal use by GNOME Games

https://git.gnome.org/browse/libgnome-games-support

Program that keeps passwords and other secrets

Graphics library for GNOME

GNOME keyboard shared library

Library and frontend for running commands as root

http://members.chello.nl/~h.lai/libgnomesu/

Libraries for the GNOME GUI, a GNU desktop environment

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/

Library for direct access to iPod/iPhone contents

http://www.gtkpod.org/wiki/Libgpod

Library for easy management of RSS/Atom/Pie feeds

http://www.gnome.org/

Extensible i/o abstraction for dealing with structured file formats

http://www.gnumeric.org

Lightweight HTML rendering/printing/editing engine

http://www.gnome.org/

GNOME top library

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

GObject bindings for libudev.

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

Library to access online weather informations

http://www.gnome.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