I just used the Universal Access zoom feature to zoom in on an icon in Mail, then used Command-Shift-4 to take a screenshot. It turns out that the screenshot that was taken is also zoomed in. Handy if you want to blow up a portion of the screen!
[kirkmc adds: I guess it makes sense that the screen shot shows the actual screen image when it's zoomed, and not the image that would be there if the screen were not zoomed. Note this recent hint explaining how to zoom with a scroll-wheel mouse or a Mighty Mouse.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061031150659735