1
Nautilus
The default GNOME file manager is great, but it can be improved with a few neat programs:
sudo apt-get install nautilus-gksu nautilus-image-converter nautilus-open-terminal
These tools improve the right-click menu in GNOME. They allow to open files and folders as an administrator, open a terminal to the folder you're in, and resize and convert images—all from the right-click menu.
2
NTFS Drives
Linux is becoming better and better at handling NTFS drives and partitions, but a couple of programs are still required if you want the best possible integration with a Windows partition:
sudo apt-get install ntfs-config ntfs-progs
ntfs-config is a crucial program that allows you to easily configure options for automounting NTFS drives. For some reason, Ubuntu does not mount internal NTFS partitions by default, so you can do that through ntfs-config. ntfs-progs is somewhat obsolete, but it's still useful if you need to fix a problem on an NTFS drive from your Linux OS.
3
Cleanup
These programs clean up unneeded caches, localizations, and backup files to save you hard disk space.
sudo apt-get install localepurge bleachbit
4
Archive
Ubuntu provides capabilities to unzip a number of different archive types by default, but a few more are critical:
sudo apt-get install unrar p7zip
That will give you the ability to unzip files in the .rar and .7z formats.
5
Desktop Effects
If you have a graphics card that can handle it, Compiz powers Ubuntu's awesome desktop effects. But by default, configuration options are pretty slim:
sudo apt-get install compizconfig-settings-manager
The CompizConfig Settings manager will let you tweak just about every imaginable setting.
6
Notifications
One of the neat new features in Ubuntu 9.04 is a standard notification system, but it doesn't work with all applications. First, grab the FirefoxNotify extension so that Firefox will notfiy you when downloads are completed. Then add the PPA here. Next:
sudo apt-get install gm-notify
That will give you notifications whenever your GMail account receives a new message.
7
Audio
Ubuntu uses the PulseAudo backend to provide audio playback. To reap the full benefits of the PulseAudio system, add the following packages:
sudo apt-get install padevchooser paman paprefs pavucontrol pavumeter
8
Hardware Management
These tools provide applets for monitoring system temperature and CPU scaling.
sudo apt-get install hddtem lm-sensors sensors-applet computertemp