Today the new stable version 5.10 of Ubuntu Linux was released!
You can read the release notes here:
http://www.ubuntu.com/newsitems/release510
You can download Ubuntu here:
http://www.ubuntu.com/download/
There is only a single 650MB installation disc in case you wonder.
Starting with 5.10 a special version for servers will be released. You can download the latest ubuntu-server from here:
http://cdimage.ubuntu.com/ubuntu-server/daily/current/
In case you are new to Ubuntu or Linux generally, this guide will get your started:
http://www.ubuntuguide.org/
(be aware that this is for 5.04 and not 5.10, the package repositories sources are not the same, so wait for the updated guide if you want to add extra repositories to Synaptic)
Have fun!