essentially, i'm looking for a macintosh equivalent to the PC Zoomplayer--a program that allows a video to be scaled down while still in fullscreen mode. Apple's DVD player allows zooming in, but not out in fullscreen. shrinking the video puts it into window mode. oddly enough, Quicktime allows this, but i really don't feel like ripping DVDs.

have you tried vlc not sure if it does this but it is my main player why do need to do this anayway do you really need more black around the pic ?

Hmm. Good question.

I don't have any Mac products that don't have an integrated display. Can you simply change to a lower resolution, and have the monitor display it in native pixels, centered? (I know I just tried this on my iMac, and it kept helpfully scaling the picture to fill the screen)
I know on my Dell monitor for my PC, that I can tell the monitor to either center or scale small desktop resolutions.

Sorry, not too much of a help I'm sure.

http://www.madrau.com/

or

http://www.3dexpress.de/