Which version of Linux is most friendly for first-time users?

I have tried Ubuntu, Knoppix 4, Fedora, and SuSE and of them I found SuSE to be the most n00b-friendly though all are adequate. I have some odd requirements and need more customization that Ubuntu allowed; maybe the new Ubuntus are better there.

Your mileage may vary.

I found Ubuntu linux to be extremely easy to learn and use, as they have a fully featured fourms on their site, and also the install cd doubles as a live cd so you can test out the whole operating system (without it affecting the hard drive at all) before you decide to install it!

In my experience, the Mandrake install process and desktop experience have been full-featured and easy to use with little or no tweaking on my part. However, different distributions always have different problems with different hardware, and sometimes even the Mandrake installer chokes on machines with older motherboards or on off-brand laptops. So it may take some trial and error to find a distro that handles your particular machine well. Some other good options in my experience include Lycoris Desktop/LX, SuSe, and good old Red Hat.

Also worth looking into is Knoppix, a distribution designed to run right off the CD without an install process to speak of. It can hang on weird hardware, yes, but it won't do any damage if it does.

The best linux distribution for newbies would be ubuntu/kubuntu, they are great distributions, but they emphasize ease of use over customizability and optimization, and perhaps even Stability in recent releases.

I'm going to assume that you mean "most friendly" from an installation point of view, because once installed, any Distro pretty well is the same, it's all just different eye candy.
Mandrake and Ubunto are both easy installs, my preference being Mandrake just because I like the look and feel working with it.

I will suggest you to try SuSE if it is compatible with your hardware other wise Mandriva is a good option.

Ubuntu is also good

I use Mint linuxKDE.It is based on ubuntu/debian.Unlike many other distros,it comes with flashplayer 9 and can play dvds right out of the box.It also can be run as a "live cd"so you can test it first.Nice!

I like ubuntu 7.04....Dell as just commisioned its use for there Linux based pcs

Ubuntu. It's based on Debian Linux but it is more good looking. You can get it here> http://www.ubuntu.com/

If you are interested in Linux, Ubuntu is a good place to start. However, if something doesnt work like its supposed to, good luck trying to figure out what you need to do to get it working. I think thats when the magic happens.

If you just want to experience linux in a safe, and enjoyable way, an amazing thing exists: KNOPPIX! You can download the cd image and burn it to a cd (under most operating systems other than GNU/Linux). Then set your BIOS to boot from the cd drive. Pop it in, and BAM! You have a linux operating system, with almost every bell/whistle. Play, learn, surf the web, etc. And you make no changes to your hard drive at all! Well, if you want to save a document or something to your harddrive, you can. But, take out the KNOPPIX cd, and reboot, and BOOM! Your back to the blue screen of death (just kidding!).

Knoppix is cool, especially because you can take it to your friends, and they don't have to be afraid. You can make (almost) any machine that can boot from a cd a KNOPPIX linux machine.

I've used Mandrake for last ~5 years and it's definitely user-friendly not only for Window$ converts but for complete noobs as well.

Long live Open Source! Java/Apache/MySQL over C#/IIS/SS any day!

For new users, I'd recommend:

Ubuntu ( http://www.ubuntulinux.org/ )
Kububtu ( http://www.kubuntu.org/ )
OpenSUSE ( http://en.opensuse.org/ )
PCLinuxOS ( http://www.pclinuxos.com/ )

Most popular Linux distributions are available free of charge. Go to their website and download an ISO disk image, and then burn the image to a CD or DVD as applicable.

SuSe linux Fedora core (3).

Definetly SUSE Linux Enterprise Desktop. It is only 50 USD and you can work with it very smootly and also it is very user friendly. You can also download eval version from http://www.novell.com/products/desktop/ It comes with OpenOffice Novell edition. So you dont need to pay for MS Office Suite anymore:)

Probably Ubuntu or PCLinuxOS.

Ubuntu automates installation of drivers and codecs, and has fantastic support in the forums. There are a couple of things you might have to set up manually though, most notably network shares.

PCLinuxOS includes all the usual codecs by default, and has a good "control centre" GUI. There's no 64-bit version though, unfortunately.

Both include 3D effects by default and come on a LiveCD so you can try it out before you install.

For users who are relatively inexperienced with computers in general and just want a working system that does not make you work too hard, I suggest either Gentoo Linux (www.gentoo.org) or Lindows (www.lindows.com). Most Linux distributions nowadays have fairly easy, straight forward installation procedures, but the real problems arise when it comes to software installation and accessing that software after you have installed it. If you are not careful, the installation process will dump a bunch of stuff on your system that you will never use or need, or you will know the program is there but don't know how to use it or even know what it does because many of these programs are not mainstream or commercial programs. Lindows and Gentoo give you easier access to mainstream and commercial programs that have been written for Linux, and their package management systems (especially Lindows) are relatively easy to use. Other operating systems, like Windows or MacOS, have only one system to manage your installed software. Linux has about a half dozen ways to manage programs, picking a management method that you can handle is very important, especially for inexperienced users.

... yet another vote for Ubuntu ...

I think the best beginner's linux distro is Ubuntu.

Though Linux Mint is good, so is OpenSUSE (for hardware detection)

Kubuntu or Ubuntu, basically they are the same but Kubuntu comes with the KDE windows manager and Ubuntu is loaded with Gnome. KDE is more "Windows like".