I'm not sure how they did it, but some crafty hacker has managed to cram a Mac Mini inside his Apple SE/30, turning his old-school Mac into a modern day all-in-one. Sure, you'll be running OS X in black and white, but think of how cool it'll look as your DVD slides out from your SE/30's front vents.
Just drop a color monitor in there too, when and if possible.
I used to build "modern" PCs in old IBM AT cases for folks years ago.
It's neat to do stuff like this, modern innards in an old chassis kinda stuff.
Especially the slot in the vents. Very nice touch.