Although ubuntu is the most polished Linux distribution, you will occasionally need to do stuff that may be out of scope of your knowledge. Here are some commercial and free resource which you can use to make ubuntu usage a breeze.
Ubuntu Linux Bible
Covers fundamental desktop and network operations. How to to use ubuntu for emailing, editing, printing, playing music & movies and games. It also offers step by step guide on how to setup wireless, how to manage your PDA and how to setup networks.
A CD-ROM comes bundled with this book. CD-ROM contains some cross platform applications like Abiword, Firefox, GIMP, etc... They work even on Windows.
Get Ubuntu Linux Bible from amazon.
Advanced Bash scripting guide
Contains A to Z coverage of how to write bash scripts, bash scripting language constructs and very useful examples.
Get Advanced Bash scripting guide as a free PDF file. Or install it using following command.
sudo apt-get -y install abs-guide
Rute Users tutorial & exposition
This book is available out of ubuntu repository and you can freely install it. It covers how to manage both Redhat & Debian based systems, shell scripting, file system, hardware, services, c programming, networking, boot loaders, servers, etc... It's a one stop shop for learning about what Linux can do and how to do it.
sudo apt-get -y install rutebook
The Linux System Administrators guide
Covers all the aspects of Linux. Install sysadmin-guide.
sudo apt-get -y install sysadmin-guide
Need any help on understanding how a particular thing works in ubuntu ?, or have a problem with your hardware ?.
Feel free to jump in Ubuntu Forums and shoot questions or IRC channel #ubuntu to get live community support.