Distributions suited for the datacenter and high-performance computing.
ClearOS is an integrated network server gateway solution for small and distributed organizations. The software provides all the necessary server tools to run an organization including email, antivirus, antispam, file sharing, groupware, VPN, firewall, intrusion detection/prevention, content filtering, bandwidth management, multi-WAN and more. Through the intuitive web-based management console, an administrator can configure local ClearOS server software along with integrated cloud-based services.
Website www.clearfoundation.com
Download URL www.clearfoundation.com/Software/downloads
Documentation URL www.clearfoundation.com/docs/

Works With Distributions Red Hat Enterprise Linux
CentOS is an Enterprise-class Linux Distribution derived from sources freely provided to the public by a Red Hat. CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes packages to remove upstream vendor branding and artwork.)
Website www.centos.org
Download URL www.centos.org/modules/tinycontent/
Documentation URL www.centos.org/docs/

Oracle Enterprise Linux
Works With Distributions Red Hat Enterprise Linux
Specifications The Oracle Unbreakable Linux program provides industry-leading global support for Linux. Oracle Unbreakable Linux support customers also have access to Oracle Management Pack For Linux and Oracle Clusterware at no charge.
Website www.oracle.com/technology/tech/linux/index.html
Download URL edelivery.oracle.com/linux

Red Hat Enterprise Linux
Works With Distributions Red Hat Enterprise Linux
Specifications Based on the original Red Hat Linux, Red Hat Enterprise Linux (RHEL) was initiated in 2003, along with the community-based Fedora Project. RHEL is primarily targeted towards the commercial market, particular the corporate server, desktop, and mainframe channels.
Website www.redhat.com
Download URL www.redhat.com/download/mirror.html
Documentation URL www.redhat.com/docs/manuals/enterprise/#RHEL5

SUSE Linux Enterprise
Works With Distributions SUSE Enterprise Linux
Specifications An enterprise-ready distribution, based on the openSUSE distribution. Novell offers product support plans, deployment services, and certification for its SUSE Enterprise Linux product line.
Website www.novell.com/linux
Download URL www.novell.com/products/desktop/eval.html
Documentation URL www.novell.com/documentation/suse.html

Pie Box Enterprise Linux
Works With Distributions Red Hat Enterprise Linux
Specifications Pie Box Enterprise Linux is derived from open source software and fully compatible with Red Hat Enterprise Linux.
Website www.piebox.org
Download URL www.piebox.org/download.php
Documentation URL www.piebox.org/docs.php

StartCom Linux
Works With Distributions Red Hat Enterprise Linux
Specifications The StartCom Linux operating systems, are based on the RedHat Enterprise and Fedora source code each modified with reliability, security and efficiency in mind, to fit the tasks assigned to each flavor of StartCom Linux.
Website linux.startcom.org
Download URL linux.startcom.org/index.php?lang=en&app=15
Documentation URL linux.startcom.org/?app=18

Specifications Turbolinux Server is a second-generation Linux operating system, incorporating the latest advances available in the 2.6 kernel, and aims to meet your mid-to-high-range server needs.
Website www.turbolinux.com
Download URL www.turbolinux.com/support/download.html
Documentation URL www.turbolinux.co.jp/support/document/manual/index.html

Yellow Dog Linux
Works With Distributions Red Hat Enterprise Linux
Specifications An open source, Linux operating system for home, office, server, and cluster users. Built upon the RHEL/CentOS core, Terra Soft and now Fixstars has since the spring of 1999 developed and maintained YDL for the Power architecture family of CPUs.
Website us.fixstars.com/products/ydl/
Download URL us.fixstars.com/support/downloads/
Documentation URL us.fixstars.com/support/installation/

Works With Distributions Red Hat Enterprise Linux
Specifications ClarkConnect is a powerful server/gateway software solution designed for the small/medium-sized organization. Though ClarkConnect comes with an extensive list of features and integrated services, the solution is easy to configure thanks to the intuitive web-based interface.
Website www.clarkconnect.com
Download URL www.clarkconnect.com/downloads/
Documentation URL www.clarkconnect.com/help/pdf/CC-Quickstart.pdf

Works With Distributions Red Hat Enterprise Linux
Specifications ASPLinux is a Russian Linux distribution created by the Moscow-based company of the same name.
E-mail [email protected]
Website www.asplinux.ru

KaOS Hypervisor
Earliest Compatible Linux Kernel
Specifications KaOS is a bare metal hypervisor based on Linux KVM. KaOS is built into the Linux kernel, installation is as easy as booting a new Linux kernel. The platform has a router/switch style menu-driven command line interface, making it easy to deploy Cloud and Virtualization solutions. The platform has advanced IP networking and an App Module framework that makes it fast and easy to build new virtual machines.
E-mail [email protected]
Website www.carbonmountain.com
Download URL www.carbonmountain.com/opensource/downloads
Documentation URL www.carbonmountain.com/opensource/kaos/

Content credit:  mp3skull