Debian - Debian is a powerful and complex Linux distribution that is not geared toward new or less experienced users.
Linux Mandrake - The Linux Mandrake distribution is well known for being easy to use and install.
Red Hat - Red
Hat's Linux distribution is the de-facto standard -- it is the best
known and probably the first place vendors go to test their hardware
and software. Red Hat is now commercial software, i.e., you must
Fedora - Fedora is the free test / development version of Red Hat.
Slackware - Slackware was one of the earliest Linux distributions and retains a loyal following among Linux enthusiasts.
SuSE - SuSE (which is pronounced "SUE-zuh") is another popular distribution.