<p>I want to learn MVC "architecture pattern" but I don't want to jump into a framework like Rails or Django just yet.  I want to understand the concept first and write some simple code in my currently familiar environment, which happens to be PHP/HTML/CSS/MySQL.  I don't necessarily need a tutorial that is based on PHP, as I do understand a lot of different languages. And I don't want to have to install any frameworks or APIs or libraries.  I just want to learn how to think in MVC and apply it to my projects. Any suggestions?</p>

Almost every framework does MVC differently, so you might end up getting even more confused. The general principles of MVC are very simple: "Model is state; view reacts to model; controller reacts to view; controller changes model". The model, view and controller are concepts - they are whatever you feel them to be. Classes, bunches of classes, instances of classes with XML configuration files, you name it.
I actually think that about covers the basic principles. Without a framework, you'd not get much further. What matters is how a particular framework defines model, view and controller and their interactions.