Want to take screenshots of a small area, and have it be a large picture? You can. Using an earlier hint about zooming in, you can take zoomed screenshots:
Hit Command-Option-Shift-8 to toggle zoom on if it's not already, then hit Command-Option-equals to zoom in to the desired region and use the screenshot keys (Shift-Command-3 or -4) to grab the screenshot. The resulting screenshot file will be exactly what was on your screen when you took the shot.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20021003054200112