Automatic font hinting library

https://www.freetype.org/ttfautohint/

MySQL performance tuning primer script

https://launchpad.net/mysql-tuning-primer

3D penguin racing game using OpenGL

http://tuxracer.sourceforge.net/

Number of fonts which are useful for TV applications

http://linux.bytesex.org/xawtv/tvfonts.html

Digital TV and radio guide

https://www.tvbrowser.org

Color emoji font using Twitter Unicode 10

https://github.com/eosrei/twemoji-color-font

Tab Window Manager for the X Window System

Simple, secure, efficient FTP server

https://untroubled.org/twoftpd/

MPEG Audio Layer 2 encoder

http://twolame.sf.net/

Converts flat ASCII text to man page format

http://mvertes.free.fr/

Ubuntu font family

https://design.ubuntu.com/font/

GPG keys for Ubuntu package signature verification

https://bugs.launchpad.net/ubuntu/+filebug

Universal charset detection library

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

Data compression library with low memory usage

https://www.oberhumer.com/opensource/ucl/

Command-line tools for building TCP client-server applications

http://cr.yp.to/ucspi-tcp.html

DNS resolver library with sync and async queries

https://www.corpit.ru/mjt/udns.html

Fast copy utility for UFS filesystem

http://people.freebsd.org/~simokawa/ufs/

HTTP web service mocking library for GNOME

https://gitlab.com/groups/uhttpmock

Convert MagicISO UIF files to ISO9660

http://aluigi.altervista.org/mytoolz.htm

Ultra lightweight xml-rpc library written in C++

http://ulxmlrpcpp.sourceforge.net/

Extract, view & test ACE archives

http://www.winace.com/

Allows files to be extracted from ARJ archives

http://www.arjsoftware.com/

Validating, recursive, and caching DNS resolver

https://www.nlnetlabs.nl/projects/unbound

Remove idle cursor image from screen

Unicode emoji data files

http://www.unicode.org/emoji

Library for single instance applications

https://wiki.gnome.org/Attic/LibUnique

Fork of Exuberant Ctags to generate index/tag files

https://ctags.io/

Local self-authentication for pam_exec

https://github.com/Zirias/unix-selfauth-helper

Convert ASCII newlines between CR/LF and LF

ODBC library suite for Unix

http://www.unixodbc.org/

BYTE magazine's Public Domain benchmark for UNIX

https://github.com/kdlucas/byte-unixbench

Extract Makeself archives

Convert any document from and to any LibreOffice supported format

http://dag.wieers.com/home-made/unoconv/

Extract, view & test RAR archives

https://www.rarlab.com/

Lists/Extracts files from a "*.tgz" or "*.gz" archive

List, test, and extract compressed files from a ZIP archive

http://infozip.sourceforge.net/UnZip.html

Zoo archive extractor

http://freshmeat.sourceforge.net/projects/unzoo/

Universal Plug and Play Software Development Kit

http://pupnp.sourceforge.net/

D-Bus daemon for simplifying power management tasks

http://upower.freedesktop.org/

Ultimate Packer for eXecutables

https://upx.github.io/

URI parsing library

https://github.com/uriparser/uriparser

URL extractor/launcher

https://github.com/sigpipe/urlview

URW core35 fonts in various formats

https://www.ghostscript.com

Another font package for X

Unicode TrueType fonts from URW extended by Valek Filippov

Database of all known IDs used in USB devices

http://www.linux-usb.org/

Daemon for multiplexing connections over USB to iPhone/iPod Touch

http://www.libimobiledevice.org

Simple, portable, lightweight library for handling UTF-8 strings

http://utfcpp.sourceforge.net/

UTF-8 processing library

https://juliastrings.github.io/utf8proc/

hash table for C structures

http://uthash.sourceforge.net/