I'm looking for an online tutorial that would show me how to duplicate the popup image effect that is done on this page below.
http://cbs2.com/watercooler/Miss.California.Christina.2.601822.html

Basically, I'd like to have the full-size image popup when the thumbnail is clicked. The popup is centered on the screen, and the opacity of the main page is shaded while viewing the popup. The popup window itself is not a standard popup, as it has no chrome or other window features other than a close button

It's called lightbox effect.
Full documentation and code here: http://www.huddletogether.com/projects/lightbox2/

Yeah what the last person said... I love the Lightbox effect.
Make sure you get the newest script (I had an older one and had some IE6 compatibility issues) and use the huddletogether forum if you run into questions.