Software I Use

avant-window-navigator
A Mac-OS-like dock. Combination of launchers and window list.

banshee
A pretty good media player (similar to iTune).

cairo-dock
A Mac-OS-like dock. More feature rich than AWN and wbar.

checkgmail
A system stray application that notifies you upon new email arrivals and allow you to do some simple actions.

colordiff
Produce a diff output with colour highlighting.

compiz
Eye-candy rich Window Manager.

conky
An application to show various system info (e.g. CPU, RAM, network, etc).  Highly configurable.

cryptsetup
Encrypt the whole partition.

d4x
A download manager.

doxygen
An application to generate HTML (or other forms of) documentation from header file documentation.

easytag
Useful software for editing MP3 tags.

evince
A light-weight PDF viewer.

ffmpeg
Media format converted. Can be used to convert video or audio from one format to another.  Can also be used to extract audio from video.

Firefox
A very good web browser.

g++
The GNU C++ compiler.

gcc
The GNU C compiler.

gedit
Default editor for Gnome (with Text Encryption Plugin).

gimp
A Photoshop replacement.

git
A source code revision management system.

gnochm
A CHM (compile HTML) reader.

google-chrome
A fast and good web browser.

gthumb
An image viewer application.

htop
Very similar to top but much much better. (see also iftop and iotop)

iceweasel
A totally free version of Firefox.

istanbul
Screen capture (movie) application.

libdvdcss2
Special library needed for playing some DVD contents.

libstdc++6-4.3-doc
Doxygen documentation for C++

liferea
A RSS reader.

manpages-dev
manpages-posix-dev
Manual pages for some development libraries.

metacity
A light-weight window manager that does window compositing as well.

mplayer
A player that plays almost all known format.

pidgin
IM for MSN, Yahoo, ICQ, QQ, Google Talk, etc.

qemu
qemu-launcher
A simple to setup and use virtual machine. Can use it to test run new versions of Linux. I occasionally use it to run MS Windows XP.

rhythmbox
Default audio player for Gnome.

scim-pinyin
Enable Chinese character input.

scim-canna
canna
Enable Japanese character input and conversion to kanji character.

screenruler
Useful when trying to align (get the distance between) web page widgets.

subversion
A RCS (revision control software) which is used primarily in controlling programming source code revisions.

tomboy
A note taking application

tora
A toad (Oracle client) replacement

totem
Default movie player for Gnome.

unison-gtk
An application for synchronizing two folders.

utorrent
An excellent BT client (runs well using Wine).

vim-gnome
The VI-improved editor.  Ideal for source code editing.

vlc
A player that comes with lots of features.

w32codecs
Codecs for playing wma and wmv files.

wbar
A simple, eye-candy type application launcher.

wine
A MS Windows emulator.  Allows you to run some MS Windows applications, including starcraft.

Xdialog
Display X boxes or windows from a shell script.

xvidcap
An application that captures all that happens on the screen into a video file.