Just Beginning
Introduction
Read this first before you try Ubuntu*

Which Ubuntu to pick?
Getting Ubuntu
Burning the Ubuntu ISO

Ubuntu inside Windows
Dual-boot with Windows
Install Desktop CD Ubuntu
Modest Specs

Install Software
Extra Repositories

Security in Ubuntu
Create a "browse as root" launcher*

Where's the Terminal?
Password in Terminal

Next Steps
Mount Windows
Install Proprietary Software
Install MP3 Playback
Finding iTunes Alternatives
Export as MP3 in Audacity
Use Wine

Beyond the Basics
Backing up Ubuntu
Upgrade Ubuntu*
Make a /home partition
Change boot menu
Install Mozilla's Firefox
Install Internet Explorer
Mount Linux

Playing Around
KDE/Gnome Comparison
Install KDE
Install XFCE
Install IceWM
Pure Gnome
Pure KDE
Pure XFCE
Make your own Ubuntu remix

Troubleshooting
No graphical login
Can't sudo
Graphical sudo
Forgot password

* Off-site link

Note
Theoretically, Ubuntu should install the MP3 codecs for you automatically, but it can't hurt to have extra repositories enabled before you start this tutorial.

This procedure will install only MP3 playback for you. If you're pretty sure you want other proprietary codecs installed, then you should install the ubuntu-restricted-extras package (which includes Flash, Microsoft fonts, and Java, among other things), as per these instructions.

Installation Procedure
First, find or download an MP3 file.

Then the easiest way to install MP3 playback in Ubuntu is to just try to play an MP3 file. So just double-click the file.

Once you do that, Totem will try to play the MP3 file and then realize you do not have the necessary codecs to play MP3 files. It'll ask if you want to search for the appropriate codec. Click Search to continue.

Click Install, then Confirm.

Wait for the codecs to install. Then click OK

Now your MP3 should start playing in Totem.