I thoroughly recommend Linux Mint 7 Main Edition which is built upon Ubuntu 9.04 Its easy to install and easy to use plus it comes with much of the software you are likely to need preinstalled
Linux Mint 7 Download
http://www.linuxmint.com/edition.php?id=38
Linux Mint 7 User Guide
http://www.scribd.com/doc/15884753/Linux-Mint-7-Gloria-User-Guide
The Perfect Desktop - Linux Mint 7 (Gloria)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-7-gloria
You download the ISO. image of Linux Mint 7 then you need to create a Bootable LiveCD for installation
Linux Mint 7 can also be run direct from the LiveCD from Booting up without touching your Hard Drive
CURRENT SESSION
Linux Mint 6 ext3 with switchable Compiz 0.7.2* and Beryl 0.2.1**
http://www.linuxmint.com/edition.php?id=31
http://en.wikipedia.org/wiki/Beryl_(window_manager)
http://en.wikipedia.org/wiki/Compiz
http://en.wikipedia.org/wiki/Compiz_Fusion
*Compiz 0.7.2 sourced from Ubuntu 8.04 LTS (Alpha 5) repositories
**Beryl 0.2.1 sourced from Ubuntu 7.04 repositories
LUg.