Set of utilities to benchmark productivity of system calls

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

Library for Microsoft compression formats

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

MusicBrainz client library for audio metadata lookup

http://musicbrainz.org/

C library for creating IP packets

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

Ogg bitstream library

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

Library providing routines for paper size management

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

Ubiquitous network traffic capture library

https://www.tcpdump.org/

PCI configuration space I/O made easy

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

Generic PCI access library

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

Library to handle Apple Property List format

http://www.libimobiledevice.org

Library that provides automatic proxy configuration management

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

Weak aliases for pthread functions

https://xcb.freedesktop.org/

RTMP stream library

https://rtmpdump.mplayerhq.hu/

Handling page faults in user mode

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

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

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

Library implementing the SSH2 protocol

https://www.libssh.org/

Library implementing the SSH2 protocol

https://www.libssh2.org/

Strigi desktop search: streams library

http://www.vandenoever.info/software/strigi/

Wrapper providing SunOS NFSv4 ACL API

Parser for SVG content in files or buffers

http://cairographics.org/libsvg

ASN.1 structure parser library

https://www.gnu.org/software/libtasn1/

Generic shared library support script

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

User space caching library

http://mercurial.creo.hu/repos/libublio

Library of Unicode annotation data

http://libuninameslist.sourceforge.net/

Library to work with RAR archivies

http://www.rarsoft.com/

Video4Linux library

https://linuxtv.org/wiki/index.php/V4l-utils

Provide an easy API to a custom vnc server

http://libvnc.github.io/

Library to provide file system type information

Audio compression codec library

https://xiph.org/vorbis/

Implementation of the XDG Base Directory specification

https://github.com/devnev/libxdg-basedir/

XML parser library for GNOME

http://xmlsoft.org/

The XSLT C library for GNOME

http://xmlsoft.org/XSLT/

YAML 1.1 parser and emitter written in C

https://pyyaml.org/wiki/LibYAML

C library for reading, creating, and modifying ZIP archives

https://libzip.org/

Secure, fast, compliant, and flexible Web Server

https://www.lighttpd.net/

Lynx-like text WWW browser

http://www.jikos.cz/~mikulas/links/

Linux-PAM offline documentation

http://www.kernel.org/pub/linux/libs/pam/

The Linuxdoc SGML DTD

Linux UPnP Internet Gateway Device

http://linux-igd.sourceforge.net/

LIVE.COM Streaming Media

http://www.live555.com/liveMedia/

Command line client for posting LiveJournal entries

https://sourceforge.net/projects/ljclive/

OpenLDAP Lightning Memory-Mapped Database

https://symas.com/lmdb/

Display information gathered from MB power management controller

Create a shadow directory of symbolic links to another directory tree

https://gitlab.freedesktop.org/xorg/util/lndir/

Legacy locale data for FreeBSD 6+

Auditing tool for system logs on Unix boxes

https://salsa.debian.org/debian/logcheck

Receive/Send files via X/Y/ZMODEM protocol. (unrestrictive)

http://www.ohse.de/uwe/software/lrzsz.html

Lists information about open files (similar to fstat(1))

https://github.com/lsof-org/lsof

Small, compilable scripting language providing easy access to C code

https://www.lua.org/

Small, compilable scripting language providing easy access to C code

https://www.lua.org/