Here is a reminder of current popular/representative Operating System run in our daily life, I hope I can spend some time to install them in Virtual environment, the classification is not regulate, just for a personal note only.

UNIX BASE:
-UNIXWare  (Commercial)
-BSD  (I don’t see anything special)
-Solaris
-Darwin/MAC OS
GNU-LINUX BASE:
-DEBIAN  (Supporting many Hardware, free software)
–Knoppix
–Ubuntu
-Gentoo base (Frequently software update and support)
-RPM base (Easy to install, popular and stable for RHEL)
–Fedora
–Red Hat Enterprise Linux
–SUSE
-Slackware base (Advance user only)
–Router / Firewall
–Smooth Wall (Very popular)
MS Windows BASE:
–Windows XP, (Vista after some years)
–Windows NT