Open source Linux OS’s: 2

Knoppix-based
Knoppix, itself, is based on Debian.
Buildix
For agile developers.
Damn Small Linux
Generally considered as the starter of mini distributions. A live CD designed for MiniCD with a hard drive install option.
Kaella
The French translation of Knoppix.
Feather Linux
Knoppix-based Linux distribution which currently fits in under 128 MB. It boots from either a CD or a USB Flash Drive, with a size suitable for a bootable business card.
Kalango
Another Brazilian Knoppix-based distribution designed to have strong visual appeal.
KnoppMyth
Specialized Knoppix distribution for easy setup of the MythTV PVR software.
Kurumin
A version of the Knoppix distribution designed for Brazilian users.
Morphix
A Live CD distribution with different flavours, including GNOME. Used as a base for many other custom live distribution such as Clusterix, PHlAK or Gnix.
Musix
A Knoppix/Debian based distribution, intended for music production, graphic design, audio, video editing, and other tasks. It is built with only free software.
More distributions based on Knoppix are listed in the Knoppix article.

Ubuntu-based
Ubuntu is based on Debian. For a list of distributions based on Ubuntu, see List of Ubuntu-based distributions.

Gentoo-based
Gentoo is a distribution designed to have highly optimized and frequently updated software. Distributions based on Gentoo use the Portage package management system with emerge.

Gentoox
An adaptation of Gentoo for the Xbox.
Knopperdisk
A new distribution aimed at USB sticks.
Kororaa
A distribution which aims at easy installation of a Gentoo system by using install scripts instead of manual configuration.
Pentoo
Penetration-testing Live CD distribution.
Sabayon Linux
Live DVD which includes a wide range of desktop environments and open-source software applications. Like Knoppix, Sabayon Linux can be installed on the hard drive.
SystemRescueCD
System rescue Live CD version of Gentoo.
Ututo
A distribution made in Argentina.
VidaLinux
A distribution which uses Anaconda as its installer.

RPM-based
Red Hat Linux and SUSE Linux were the original major distributions that used the RPM file format, which is today used in several package management systems. Both of these later divided into commercial and community-supported distributions. Red Hat Linux divided into a community-supported distribution sponsored by Red Hat called Fedora, and a commercially supported distribution called Red Hat Enterprise Linux.

Fedora-based
Aurox
Young Polish distribution with emphasis for multimedia, graphics, localization and education.
Aurora SPARC Linux
For Sun's SPARC architecture
K12Linux and K12LTSP
A distribution for educational purpose. K12LTSP comes with LTSP support.
Linux XP
Focuses on ease of installation and use.
Linpus Linux
Focused on the Chinese market and EEE PC like computers (Linpus Lite).
Yellow Dog Linux
For the PowerPC platform.

Red Hat Enterprise Linux-based
Asianux
A distribution co-developed between Red Flag Software Co., Ltd., Miracle Linux Corp. and Haansoft, INC., focused on Chinese, Japanese and Korean supports.
CentOS
Community-supported distribution that aims to be compatible with Red Hat Enterprise Linux without the inclusion of proprietary software.
ClarkConnect
Router/firewall distribution
Scientific Linux
A distribution co-developed by Fermi National Accelerator Laboratory and the European Organization for Nuclear Research (CERN), which aims to be compatible with and based on Red Hat Enterprise Linux.
SME Server
Based on CentOS and targeting Small and Medium Enterprises.
White Box Enterprise Linux
A distribution designed to be compatible with Red Hat Enterprise Linux.
See Red Hat Enterprise Linux derivatives for a more complete list, as well as Commercial products based on Red Hat Enterprise Linux.