Ubuntu 10.04 Lucid Lynx is on its way for a public release. Here's a list of 6 applications that you must have on your Ubuntu system if you are installing the  operating system afresh or if you don't have them already. But before that the basic.

How to install an application in Ubuntu?

a) From Ubuntu Software Center: Go to Applications > Ubuntu Software Center and search for the application or tool in the list. Click install. Can't get any easier. If it's not available in the software center, download a .deb package of the application and run. (Deb packages are Ubuntu or Debian Linux equivalent of .exe installation files in Windows.)

b) Using the Terminal and command line: If you want to be geeky, you can use the command line for installation. Go to Applications > Accessories > Terminal.

Type the command: sudo apt-get install application-name.

If you want to uninstall, replace install with remove: sudo apt-get remove application-name.

Ubuntu restricted extras/Gstreamer plugins

Ubuntu does not ship with in-built support for various media formats such s .mp3, .mp4, flash and Java files. Ubuntu restricted extras will add codec and file to support them and enable you to enjoy your music collection without any hassle.

Gstreamer plugins for adding media support is available in Software Center channel, so it's more convenient to install.

sudo apt-get install ubuntu-restricted-extras

VLC Media Player

VLC is undisputedly one of the most versatile multimedia player. It will play almost everything: mp3s, videos, flash, CDs and DVDs.

sudo apt-get install vlc

GIMP Image Editor

If you have a digital camera or a phone camera, you should install GIMP. Earlier, it came pre-loaded with Ubuntu, but now it has been categorized as a geeky application that's used by medium to advanced users. That's why it has been kept out of the default applications. GIMP is a Photoshop alternative that comes handy when you need to process your images or makes some interesting collage.

sudo apt-get install gimp

Gnome Do

Starting a new application can sometimes be a pain. You need to first go to the Applications menu, then to the appropriate segment and search for the entry. Launchy or Gnome Do application launchers will ease the pain.

Gnome Do makes the process of launching new applications a breeze. Just start typing the name of the application and hit enter when you get the desired one in the Gnome Do's eye-candy suggestion window. Or else type the first letter and then use down arrow key to choose from the available options. Gnome Do can also be used for searching your files and folders, chatting with friends or sending a tweets, thanks to plug-ins that come with it.

Gnome Do can be dowloaded from the Ubuntu Software Center. Once installed, you will have to configure it on its first run. Click on the small down arrow to choose Settings from the menu. Check "Start Gnome Do at login", "Hide window on first launch" and "Show notification icon" in the General tab.

In the Keyboard tab, you will see that the hot key for calling and hiding Gnome do is set as <Super> <Space>. What's <Super> key? It's the Window or Command key. If you want to change the shortcut to, say, <Ctrl> <Space>, double click on the shortcut and press the two keys of your choice simultaneously.

In the Plugins tab, choose the ones that you want to activate. In the Appearance tab, you can check "Always show results window". Now your Gnome Do is ready to serve at your slightest hint.

Launchy is another application launcher, but it's lacks some features of Gnome do. The default hot key for calling Launchy is <Ctrl> <Space>. If you want to be able to use Launchy on top of other applications, click on the configuration icon (looks like a gear) and tick the "Always on top" option.

Launchy is not available in Ubuntu software channel and will have to be downloaded from its website. If you are using a computer with Inter processor, download Launchy_xx.xx_i386.deb file. If your's is an AMD computer, download Launchy_xx.xx_AMD64.deb. After downloading, run the installer. You will find Launchy in the Applications > Accessories channel after successful installation.

Google Chrome

Google's new web browser is making its place among users with its speed and its growing list of add-ons. Even if you are more comfortable with the default Firefox Web browser, installing Google Chrome will only do good as an alternative browser. Google Chrome is also not available in the Ubuntu software channel, and will have to be downloaded from its website.

Opera is also a good alternative Web browser, with focus on bells and whistles.

Ubuntu Tweak

Though I have listed Ubuntu Tweak at the end, it's the one which you should install first. Ubuntu Tweak comes handy in easily managing and tweaking the settings of an Ubuntu system. It allows you to install and uninstall applications, choose display settings and manage your desktop settings, among others. It can also be used too install a large number of application (including some of the above listed ones) easily using the graphical interface. It also includes Compiz Settings Manager.

Go to Ubuntu Tweak's download page and use any one of the listed methods for installing the tool. I would suggest you follow the link to download the latest .deb package and run it on your system.