I don't know if the original Unix is still used that much but there are many unix-like operating systems in use today: OS X, Linux, FreeBSD to mention a few.
I actually only know the name of one operating system that is not "unix-like" and that's Windows, so I think you can say that unix-like operating systems are used almost everywhere.
There are quite a large variety of Unix based systems...
Solaris also makes a version of Unix that is still in distribution...
But here is a link that will show you the most recent versions for you...
http://distrowatch.com/