The best known as a LiveCD (as opposed to being the most popular with a LiveCD available) is Knoppix.
Most of the popular Linux distributions these days have a LiveCD portion, including Ubuntu, PCLinuxOS, and even Gentoo. The most popular known specifically for LiveCD functionality is probably Knoppix.
Linux Security Tool Distribution (STD) is really good.
Get the Ubuntu (linux) version. If you install ubuntu it comes with it.
Red hat linux is the best to learn and use if you want a stable operating system.
Linux.
The newest one. As of February 2009, that would be Sabayon 4.0.
It depends on what you plan to use it for.Right in this moment it is 2.6.33-rc8-git7
Linux (ubuntu 10.10 and higher) and mac OS x (newest version) because they're the fastest best looking and simplest.
For desktop computers, Canonical's Ubuntu, Linux Mint and Fedora are all very strong distributors for the operating system while for laptops, Fuduntu is a well known and good distributor for Linux.
Linux does not need antiviruses. It doesn't as much as windows, but it is possible for you get a virus on this system. Avast has a version for Ubuntu and its branches of distros. http://www.avast.com/linux-home-edition
Yellow Dog Linux is the only operating system officially endorsed by Sony. However, the necessary support for the PS3 hardware has already been integrated into the Linux kernel, so almost any PowerPC version of Linux can be used. The other popular choices are Ubuntu, Debian, and Fedora.
The best known version was recorded by Elvis Presley.