Ubuntu
Ubuntu was at one time the de facto standard Linux distribution for new users, but thanks to Ubuntu Unity, that title has been stripped away. This doesn’t mean Ubuntu is useless. In the next year or so, Ubuntu will come out with the first straight-up Linux tablet, and Unity’s true purpose will shine through. Ubuntu is still a good distribution for new users.
http://www.ubuntu.com
Ubuntu 12.04 LTS (Precise Pangolin) (Beta)
Linux Mint
This is the de facto standard for new users. Linux Mint took everything that was great and user friendly about Ubuntu and added its own take on GNOME 3. This combination made for an incredible environment for first time (and old time) users of Linux.
http://www.linuxmint.com/
Linux Mint 12, codename "Lisa"
Fedora
If you want a more bleeding edge Linux, Fedora is the distribution for you. Also, if you want a more pure take on GNOME 3, you want Fedora. Since Fedora is cutting edge, you can expect to do a bit of tweaking here and there.
http://fedoraproject.org/
Fedora 16
Debian
If you’re looking for a good development environment, you want Debian. It’s the distribution Ubuntu was found upon and is a rock solid flavor of Linux. And with the apt package management system, it’s fairly easy to manage.
http://www.debian.org/
Debian Squeeze (6.0.4)
Puppy Linux
Puppy is that tiny Linux distribution you use when you have a low-powered machine or need a machine for a specific purpose (such as running VirtualBox virtual machines, network scanning, or hard disk rescue). Although Puppy Linux can be used as a desktop distribution, you might find it frustrating to get exactly how you need to do the work you want to do.
http://puppylinux.org/
Puppy 5.2.8 Lucid
OpenSuse
Get KDE here. Get a solid package management and system admin tool here. New users need not necessarily apply. As for a specific user group to associate with openSUSE, that’s a tough one, but I think anyone needing multi-lingual support and something other than a variation on GNOME should try it.
http://www.opensuse.org/en/
openSuse 12.1
CentOs
If you want the serious power of enterprise Linux without having to pay for Red Hat Linux, you want CentOS. Mail servers, Web servers, DNS, DHCP… you name it, and Cent OS can do it. And, unlike Red Hat, there is no price associated with CentOS.
http://centos.org/
CentOS-6.2
Red Hat Linux
This is the Mac Daddy of Linux distributions. Not only is Red Hat the distribution for enterprise and corporate environments, it is also the first Linux company to make a serious profit. With Red Hat Linux (and its fairly steep price), you will get plenty of support and some proprietary software to make the management of that server/network/environment so much easier.
http://www.redhat.com/
Red Hat Linux 6.2E
This Wiki Article gives an overview of all the distros:
