Live CDs - a way to choose your distro
A Live CD allows you to test-drive the usually latest stable version of KDE SC without the need to install Linux or to change your existing Linux installation. These distributions boot and run completely from the CD and don't modify your hard disks. They can therefore be tried on a Windows computer without risk. All listed CDs are freely available for download.
KDE Neon is a KDE project that provides the latest versions of KDE software on top of the latest LTS version of Ubuntu. There are two versions of KDE Neon: the User Edition that comes with the latest released versions of KDE software, and the Developer Edition based on pre-release versions. With the Developer edition you have the choice between using the stable or the unstable branch.
A live CD version of Kubuntu. Kubuntu is a community distribution based on Ubuntu.
openSUSE no longer offers a live cd of its regular distribution. However, there are live cd's based on the regular distributions but giving you the very latest development versions of KDE software:
openSUSE Argon is based on openSuse Leap (the stable distribution) while openSuse Krypton is based on openSUSE Tumbleweed (the rolling distribution).
A fast paced distro targeting users who want the latest and greatest available in the world of FOSS. Fedora KDE usually has the latest stable version of KDE in the repositories, and beta versions are usually shipped via supported extra repositories.
Originally based on Arch Linux, Chakra is focused solely on KDE workspaces. It is possible to install third party applications, as well.
Mageia is a community based distribution. It is a fork of Mandriva.
Netrunner is based on Kubuntu with it main focus on KDE, and aims to be complete operating system for both beginners and experts.
KaOS is a "rolling release" distribution focused on KDE.
Sabayon is a "rolling release" distribution, meaning that you install once and have your system upgraded as new versions of installed software is added to the distribution. Perhaps not the easiest distribution for users new to Linux.
Korora aims to be easy for new users, but still useful for experts. It is a community project based on Fedora.
Based on Mandrake (now known as Mandriva).
An Indian project, SuperX is based on Ubuntu. From the project site: SuperX uses a tweaked version of KDE and is aimed towards beginners, casual users and business looking for a well supported user-friendly Linux OS.
ROSA, a Russian company, offers their enterprise solution ROSA Marathon 2012 for download. The new ROSA Desktop.Fresh edition is aimed at regular desktop users.
Slax - Live CD
Based on Slackware. With modular structure and pseudo read-write CD filesystem. Slax can be run from a USB Flash Drive. Slax has no graphical installer; if you want to install Slax on your machine, you must follow the simple instructions in the Introduction document.
KXStudio has a focus on audio and video production. Currently, it is based on Ubuntu and has KDE as its officially supported desktop.
Pisi Linux is Turkish project building on the original Pardus project. Pisi Linux is a community project.
OpenMandriva Lx aims to be easy to get started with but also cater to the advanced user. OpenMandriva is a community project.
Designed to run from a USB flash drive, Porteus is small and fast. Porteus is a community project based on Slackware.
Another KDE-only distribution based on Debian.
New Live CDs and DVDs are becoming available all the time. If you've heard of a distro and think you'd like to try it, do an Internet search for it. You may well find that a Live CD is available.