the most popular distributions that i know of are these:
1. RedHat Fedora Core Distribution - Fedora would have to be the most popular beacause its very easy to use and very easy to install
2. Ubuntu - Like fedora, this distribution is very easy to use and has very good support
3. SuSe - i never installed Suse before, so i dont know
4. Caldera
5. Debian
there are other but these are the ones i can think at the top of my head. :)
| Distribution | Features | Platforms | Web Site |
| Fedora Project | the inheritor of the previous red hat distributions, the entirely open source fedora features tools and useful in any linux environment. includes GNOME, KDE and RPM desktops | I386 | redhat.com |
| Red Hat Enterprise | This package and several variants represent the latest iteration of what had before of the standard linux distributions a carefully managed upgrade program intends to bring greater stability and integration to business users. this system is not available for free. its not open source | x86, itanium, Alpha, SPARC, Mainframe, M68k | redhat.com |
| SuSe Linux | this distro is from germany and its freely available and offers software packages for many business needs. comes with GNOME KDE and RPM | x86, itanium, Alpha, SPARC,PPC | suse.com |
| Slackware Linux | this distro come with GNOME and KDE. prides itself on being "UNIX-LIKE." | x86, ALPHA, SPARC | slackware.com |
| Debian Linux | debian offers the largest number of packages of all distros. it contains software packages for any use and ships with GNOE KDE, the debian package manager and RPM | x86, ALPHA, SPACK PPC | debian.org |
| Turbo Linux | this is the most common distro used in asia. it is famous for its clustering abilities. it comes with GNOME KDE and RPM | x86 itanium ALPHA mainframe | turbolinux.com |
| Mandrake Linux | this is a user oriented distribution similar to red hat with enhancements for ease of use. it comes with GNOME KDE and RPM | x86, PPC | linux-mandrake.com |