A new feature in Leopard is that when you take a screen shot of a window using Shift + Command + 4 then hitting the Space bar and clicking on a window, the screen shot includes the drop shadow of the window. This generally makes the screen shot look nicer. But depending on how you plan to use your screen shot, the drop shadow can be a problem. If you want to take screen shots of entire windows without having the drop shadow, here's how to do it.

Open up a terminal window and enter this command:

defaults write com.apple.screencapture disable-shadow -bool true

You then need to log out for this change to take effect. But after that, your screen shots will no longer include drop shadow.

If you decide that you want the drop shadow back again, repeat the command but replace the true at the end of the command with false.