Peter
So Ubuntu Hardy Heron has now arrived, and you can download the new release from the Ubuntu site.
The main desktop release tends to overshadow the other projects that are official variants of Ubuntu. If you're new to the distro, new to Linux in general, or just want a refresher, here's what is available as well as the standard desktop product.
Ubuntu Server Edition
Server Edition, is, quite obviously, the version of Ubuntu tailored for running servers. Instead of being a graphical live CD, the Server version boots straight into a text-based installer, then sets up a system optimised for common server tasks.
You do have full access to the Ubuntu software repositories, so it is easy to then customise it to do whatever you need it to do.
Hardy Heron Server Edition is a Long Term Support (LTS) release, and it will be supported until 2013.
Kubuntu
Kubuntu is the official Ubuntu derivative which ships with the KDE desktop environment, rather than the GNOME desktop which comes with the standard version. I personally run this KDE variant on my desktop, although I also work with GNOME a fair bit too.
Hardy Heron actually brings two different Kubuntu releases to the table. The standard desktop PC version features KDE 3.5.9 which is less bleeding edge and is more tried-and-tested technology. There is also a 'KDE 4 Remix' disc available which features the same Ubuntu base with the newer, but less stable KDE 4 desktop. I plan to be looking at this KDE 4 Remix disc in more detail in an upcoming post.
Unlike its GNOME counterpart, the Kubuntu distro does not have the LTS tag, meaning it will only be supported for 18 months.
Xubuntu
Xubuntu uses the more lightweight Xfce desktop environment, which makes it ideally suited to lower-spec computers that might be sluggish running the main edition, or the KDE variant.
Xubuntu does have Long Term Support, and because it is a desktop release, Hardy Heron Xubuntu will be supported until 2011.
Edubuntu
Edubuntu is a derivative specially designed for use in education and schools. It is preinstalled with many educational applications and other specialised software such as the iTalc classroom management system.
Edubuntu does not have Long Term Support at this release, so it only has the standard 18 month support cycle.
Gobuntu
There are some elements of Ubuntu that aren't 100% free software/open source. Mostly these are 'restricted' drivers that are used in certain hardware configurations, that make Ubuntu able to support hardware for which there isn't a free driver available.
However, some people prefer to run an operating system that is 100% free software and open source, and Gobuntu is the official Ubuntu derivative that offers that.
Right now it is still quite early days for Gobuntu, and there is only a text-based installer. "Please note that because running Gobuntu on most laptops and many desktops will be difficult, Gobuntu is intended for experienced Linux enthusiasts at this time."
Still, if going pure is your thing, Gobuntu is worth a try.
Others
This list only encompasses the official derivatives that are part of the Ubuntu project. In reality, there are many more distros that have used Ubuntu as a base and built on top of them, but which have diverged from the Ubuntu project itself.
There is also one more that I haven't mentioned in this list - Ubuntu Mobile Edition. Its focus is more towards specific mobile devices and so I didn't include it directly here.
Hopefully this clears up the inevitable confusion as to which 'buntu is which. Most people will probably just want to try the standard desktop version, which you can always grab a copy of at this page. For the more adventurous, and those with specific requirements, however, some of these versions could be a perfect fit.
