As discussed in this macosxhints blog entry posted by Kirk McElhearn during my absence last week, OS X 10.4.8 includes new control-scroll access to OS X’s screen zooming feature. (The screen zoom portion of the hint isn’t new—it’s been around for many years now, hiding in the Universal Access System Preferences panel.)
As long as we’re talking about screen zooming, though, here’s a related hint: you can capture a zoomed-in screenshot. This could have practical value in presentations, books, or blog articles—there’s nothing like a zoomed-in shot to really show the audience what you’d like them to see. Beyond the practical, though, it can also just be somewhat fun to grab shots of a zoomed-in screen.
There’s really not much complexity to this hint—just use OS X’s normal screen capture tools (Shift-Command-3 and Shift-Command-4) while zoomed in, and your screen capture will reflect the screen’s zoom level, as in this screenshot:

The only caveat is that you can’t use the “capture a window” screenshot mode (invoked by pressing the space bar after hitting Shift-Command-4) on a zoomed-in window. It’s not that it won’t work; it will. But what you’ll capture is the window at 100 percent, not in its zoomed in state.
On a dual monitor setup, capturing a full-screen screenshot via Shift-Command-3 might give some odd results. On my system, the screen with the menubar was shown in its zoomed-in state, but the second monitor was shown at 100 percent (but it was distorted, as though the system tried to adjust for the fact that the image was a different size on the main screen). So this trick is most useful with the capture-region (Shift-Command-4) screen capture modes, letting you quickly grab a zoomed-in sample of any portion of your screen.