software for Unix, &c.

Only free software is listed on this page, unless otherwise marked (≠).

These are mostly command-line tools (though some may also have graphical interfaces, and specific support for other operating systems). Software intended to be used primarily under the X window system is marked with an X.

unfiled

Remind
language and interpreter for creating reminders and calendars
TestDisc & PhotoRec
data recovery software
tmux
terminal multiplexer (in preference to screen)
Plan 9 from User Space
the successor to Unix, ported to Unix
LillyPond
high-quality music printing (for European classical notation)
MuPDF
X : small/fast PDF (& XPS) viewer
Evince
X : document (PDF, &c.) viewer (when MuPDF is not enough)

text

mawk
a very fast (if not the fastest) implementation of awk (often faster than GNU sed!)
minised
a smaller, cheaper, faster SED implementation
icdiff
improved coloured side-by-side diff
ShellCheck
a static analysis and linting tool for sh/bash scripts
Pandoc
convert from one markup format to another
peg/leg
recursive-descent PEG parser generators for C
ANTLR
ANother Tool for Language Recognition (also: ANTLRWorks GUI)
Code Browser
X : a fast/functional/clean folding text editor (supports elastic tabstops)
Textadept
X : a fast, minimalist, Lua-extensible text editor (supports elastic tabstops)
Geany
X : text editor with a small and fast IDE
Meld
X : a visual diff and merge tool
Fontmatrix
X : font manager
FontForge
X : outline font editor
Microsoft ClearType fonts
≠ : a script to install the excellent fonts included with Windows Vista

network

HTTrack
website mirroring; a welcome alternative to wget
Claws Mail
X : fast/lightweight and extensible e-mail client
dwb
X : comprehensive keyboard driven Webkit browser
xombrero (xxxterm)
X : minimal Webkit browser with built-in cookie/script control
Transmission
X : BitTorrent client

system

htop
an interactive process viewer (like top)
ranger
excellent text-based file manager with Miller columns
ncdu
fast disk usage analyzer with an ncurses interface
earlyoom
user space oom killer (because the kernel’s waits too long)
PowerTOP
measure power consumption of running software
xdotool
X : command-line tool to simulate keyboard/mouse input, move/resize windows, &c.
AutoKey
X : desktop automation utility (text substitution, hotkeys, scripts)

audio/video

SoX
digital audio conversion tools (with accurate resampling)
FLAC
Free Lossless Audio Codec
abcde
comprehensive CD encoder
mpg123
small, fast mp3 console-based player for files and streams
Music Player Daemon
audio server
StreamRipper
save mp3 (and ogg) streams to file
FFmpeg
record, convert and stream audio and video
MPlayer & MEncoder
movie player & encoder
VLC
multimedia player/server
gmusicbrowser
X : music browser/player for large collections
EasyTAG
X : tag viewer/editor for most audio file formats
Ardour
X : digital audio workstation
Pd (Pure Data)
X : real-time graphical programming environment for audio, video, and graphical processing
SuperCollider
X : environment and programming language for real time audio synthesis and algorithmic composition
Processing
X : programming language and development environment for visual arts

pixels

gphoto
manipulate digital cameras
GraphicsMagick
image manipulation tools (originally forked from ImageMagick)
scrot
X : screen shot (capture display state)
darktable
X : photography workflow application; enhance/develop raw images
Scan Tailor
X : interactive post-processing tool for scanned pages

illustration

Asymptote
vector graphics language that provides a natural coordinate-based framework for 2D and 3D technical drawing
Context Free
environment for editing, rendering, and exploring images generated from design grammars