Which is the most popular version of Linux offered for 2007?
I need to take a course in Linux.

Tricky question to which everyone has an answer. Mine is: probably Ubuntu - www.ubuntu.com

Check the top ten at distrowatch for more common ones.

edit: I've also asked one of the moderators to move this to another section as Linux from Scratch is a distribution already, not a stage in your Linux experience

Most popular is a tricky question as noted above.

Personally I prefer Fedora. All the distros have their own adherents so questions like this get you opinions rather than fact.

I once saw some idiot post that the fact he saw more Fedora questions than Ubuntu questions proved that Fedora was inferior. I pointed out that it more likely means there are a lot more people using Fedora so a lot more people to ask the questions.

Also you have families of distros. e.g. CentOS, Fedora and RedHat are basically RedHat derivatives where as Debian, Ubuntu, Kubuntu are all Debian derivatives.

I agree with JD. I run Red Hat on the servers I manage, and Fedora for home use. It has all the bells and whistles I need. I've actually grown fond of the rpm package management utility. It does make things easier for someone just starting out.

Based on what you can hear from websites on the subject, Redhat is most popular for businesses, while Ubuntu is most popular for personal use (though numbers are never quoted).

If you're hoping to use this education for potential future employment, learn Red Hat. While taking the course, triple boot your home computer with Windows, Red Hat, and Debian 4.0. When learning how to do something in Red Hat, also study on your own how to do it with Debian.

Ubuntu is (seemingly) more popular than Debian, but you'll learn a little more doing things in Debian than doing it in Ubuntu. More or less, all Debian experience will be directly applicable to Ubuntu, but not necessarily the other way around. Debian lacks some graphical tools that Ubuntu has, but Ubuntu retains the options to configure things directly via "the Debian way".

Currently, Red Hat is the leader in business, but Debian has a large presense also and Ubuntu is a serious contender rising like a skyrocket. You'll be prepared for virtually any Linux job with a background in both Red Hat and Debian.

Arguably some SuSE experience wouldn't go amiss either.

Without trying to change the intent of this thread from "which disto is the most popular" (see the distowatch link above) to "which disto do I like best", I'd like to put in a (small) plug for Mandriva 2007.1 too.
It's origins are from Fedora/RedHat (hence, it uses RPM to manage packages), is KDE based, and sort of fits into a nitch where it's both useful for enterprise and for at home/desktop.
I say that because I had tremendous success using the 2005 and 2006 "free" versions to link remotely with both Sun workstations and Win2003 servers at work. I was blown away by the instant productivity increase generated by the flexibility I gained by working from home.

It's true that Mandriva has fallen off in popularity in the past 18 months or so, mostly due to a couple of mediocre decisions (read: Cat), a more-buggy-than-expected release (ok, maybe 1 and a half) and one starry eyed penguin.
But the reaction to the 2007.1 (Spring) release has been more than favorable. It's good. The installer is still one of the best around, and the very intuitive disk-partitioning is without equal.
[just my $0.02)

Moved: Not LFS related.

I would like to add a distro which has not yet been mensioned, but i think that it should be.

I use slackware (one of the first ever LINUX distros)

It is a very stable system and works very well on any system. But is not always recomended for newbies, but I believe that a newbie should not overlook this distro. With this distro you have to get 'down and dirty' with a lot of config files and edit things yourself. But if you want to learn how to use LINUX, then this is the best way to do it.
Use slackware for 6months, and by the end of it you will know so much, that switching to a more userfriendly distro will be childsplay and you will know everything that you will ever need to know about how to set up and configure a linux computer.

I hope that in this reply, i have made some sense and have helped you narrow down your choices.

Just above this topic various subforums are listed with the number of people currently browsing each. Judging from that, most popular is Slackware (73), then Fedora (56), then Suse (45), then Ubuntu (34), then Debian (29). Or it could mean many Slackware users get in trouble and need help, Fedora is next most difficult, and so on.

The reason for the high number of slackware users is likely down to the fact that LinuxQuesions hosts the official slackware forum.

The logic you've applied is probably difficult to interpret - there could be any number of reasons why there are a certain number of users in a particular forum. For example, I think that the latest version of Fedora Core was not long ago released, which is likely to generate a lot of questions, hence lots of people in that forum. The same logic may be applied to any number of the other forums.

A more apt indicator might be the number of downloads of a particular distribution; such figures are available at distrowatch.com.

The trouble with Linux is there's no central body, which is why this question is most often answered with opinions rather than facts (as I did above ).

I would like to add to the above post:

Slackware is one of the oldest distro's and so has a LOT of users, so more users = more questions = more people in forums