I discovered this by accident. The Mighty Mouse has a very smart soft zooming capability enabled by pressing the "crtl" key while scrolling with the ball.
Incredibly smooth... and fun when you use that to have PhotoBooth as full screen !
for everyone else, try apple+alt+8, to turn it on (make sure it's set up right in the Universal Access pane of System Preferences), and apple+alt+= and apple+alt+- to zoom in and out.
i use this a lot to view embedded movies in webpages full screen.
Try Command + Option + Control + 8.
(apple, alt, ctrl, 8)
Screen should go white against black - though many european apples with german, spanish, italian etc. as a OS language might use a different key combination.