First of all these are not versions but distributions.
Listing every linux distribution in existense is not something importand or even clear, exactly because making a linux distribution is something fairly easy, anyone can make his own distribution that will provide the facilities that he sees fit (the difficult part is to make a good distribution that will provide facilities that different people need, and keep it good!). This is easy to understand if you consider the fact that Linux (GNU Linux to be more accurate) is a prototype operating system that uses a number of free applications (one application in example is the Linux kernel, some others are to provide a graphical enviroment, etc). These applications exist free on their own, anyone can pick them and put them together in an organized way to provide a fully functional operating system, as soon as he reads a few things about what they do, what they need and how they work. This is exactly what the distribution developers do, they choose free software applications and put them together after they make sure they work fine, and then they provide them to you as a unified Linux Distribution.
It is importand if you want to work with linux, to understand that it is not one monolithic operating system like windows, where the kernel and a number of specific applications authored by microsoft are offered like one big software that can not be divided (Windows) -which by the way may seem natural and good, but if you think better about it, it takes away from you the capability of choise and unecessarily forces you to accept (and pay for) one big vendor's (microsoft) choises-. In Linux it is not like this, any Free software you have chosen to install is part of your operating system, because the operating system is actually nothing more than this collection of free software! Moreover, it doesn't work like this just because somebody decided it (though somebody did, Richard Stallman back in 1983), it ended up as a success only because the end users decided that this is the most natural and efficient way to offer something like an operating system when the only priority is quality instead of making money. [rant]Windows model ended up monolithic like this, because Microsoft corporation decided that this would be the most financially beneficial to do: it would justify a larger selling price as it would be "something big" and it would also prepare the ground for other future and indirect profits by making popular their proprietary technologies and software -once they were popular enough everybody's hands would be tied to (pay to) use it or risk losing market's percentage. [/rant]
Anyway, the various Linux distribution authors do just that, they merelly provide you with an interface (the installation wizzard) that allows you to put together as many of the many many pieces of software you want, to form an operating system with the facilities you want. No matter what distribution you choose, in the end you will have the same operating system: "Gnu Linux", there are only some differences that may seem big in the beggining, but as you understand better how things work (which you will have to, undoubtly, no matter the distribution) you will see that they are technically but minor details. Most importand of these, are the pieces of software that the distribution authors have chosen to force you (or more correctly encourage you strongly) to use, as they help you with some tasks that you will need to do in a frequent basis. An example of such "detail" is the Package Manager. The package manager is the piece of software that handles the tricky task of keeping track of what other pieces of software you have installed on your operating system, and allowing you to add, remove or upgrade any of these easily and without incidents that could occur from dependency relations among them. Most distributions offer Package Managers that are somehow different in the way of use, but they do the same thing.
I didn't say all these to underestimate the work of distribution authors -which is critical and difficult no doubt-, just to help you understand how things are and that choosing a linux distribution is not the most importand thing and will in no case define what you will and will not be able to do.
Appart from that, depending on what you are up to, you may feel more comfortable to make your first steps with the choises of a specific distribution. There is no definite answer of what to choose, everyone will have a personal favourite to recommend you! Personally I strongly recommend you to begin with Slackware and after you gain some experience try Gentoo. Other popular choices that I can think of are Fedora (what is left of Redhat), Debian, SUSE and Mandrake