I am wondering if it is possible to run Mac OS X on a PC.  Since OS X
is UNIX based I would think that it could be run on any machine.  Is
this the case?  I am aware that it is possible with earlier versions
of the MacOS if you used some sort of emulation program.  Can OS X be
run on a PC without some an emulator?

The short answer is no.

Earlier versions of Mac OS ran on 68k emulators. There are no
*feasible* PPC emulators because it's just harder to get a CISC to map
to an RISC instruction set.

Darwin (the core of Mac OS X -- sans the Aqua GUI) however, will run
on PCs. It's freely available here:
http://developer.apple.com/darwin/

It's a variant of FreeBSD:
http://www.freebsd.org

That's true.  While UNIX is at the core of OSX, there are a bunch of
Apple proprietary stuff (ie-not part of the open source initiative)
that runs on top and makes OSX more than just UNIX (such as
Quicktime).

Currently, there is no way to get the entire OSX experience on PC
hardware, although given the NextSTEP heritage of OSX, porting should
pose little problem and there is constant speculation that Apple has
an internal parallel build of OSX that can run on Intel processors,
just in case they ever decide to switch chip platforms.