Hey, I thought I would make a list of all current Linux/Unix OS with their respective description (wikipedia for most of them) D:
Debian : http://www.debian.org/
Debian is an operating system composed of free software mostly carrying the GNU General Public License.
Debian systems can use either the Linux kernel (known as the Debian GNU/Linux distribution), the FreeBSD kernel (known as the Debian GNU/kFreeBSD distribution) or, more recently, the GNU Hurd kernel (more precisely, the GNU Mach microkernel and its servers; known as the Debian GNU/Hurd distribution).
Ubuntu : http://www.ubuntu.com/
Ubuntu is a Debian-based Linux operating system, with Unity as its default desktop environment. It is based on free software and named after the Southern African philosophy of ubuntu (literally, "human-ness"), which often is translated as "humanity towards others" or "the belief in a universal bond of sharing that connects all humanity".
Linux Mint : http://www.linuxmint.com/
Linux Mint is a Linux distribution for desktop computers, based on Ubuntu or Debian. Linux Mint is aimed at being a "modern, elegant and comfortable operating system which is both powerful and easy to use." Mint provides full out-of-the-box multimedia support by including some proprietary software such as Java and Adobe Flash. Mint's motto is "from freedom came elegance".
Slackware : http://www.slackware.com/
Slackware is a free and open source Linux distribution. It was one of the earliest operating systems to be built on top of the Linux kernel and is the oldest currently being maintained.
Slackware aims for design stability and simplicity, and to be the most "Unix-like" Linux distribution, making as few modifications as possible to software packages from upstream and using plain text files and a small set of shell scripts for configuration and administration.
Fedora : http://www.fedoraproject.org/
Fedora formerly Fedora Core, is an RPM-based, general purpose collection of software, including an operating system based on the Linux kernel, developed by the community-supported Fedora Project and owned by Red Hat. The Fedora Project's mission is to lead the advancement of free and open source software and content as a collaborative community.
Gentoo : http://www.gentoo.org/
Gentoo Linux (named after the Gentoo Penguin) is a computer operating system built on top of the Linux kernel and based on the Portage package management system. It is distributed as free and open source software. Unlike a conventional software distribution, the user compiles the source code locally according to that user's chosen configuration.
OpenSUSE : http://www.opensuse.org/en/
openSUSE is a general purpose operating system built on top of the Linux kernel, developed by the community-supported openSUSE Project and sponsored by SUSE and a number of other companies.
They are more OS but for now those are the most used and active(community), if you have others OS in mind feel free to post it, I will add it on the main post