Leopard has a new unwelcome (to me, at least) feature -- a shadow around whole-window screenshots (ie, Command-Shift-4, Space). Fortunately this can be disabled from Terminal with this command:
defaults write com.apple.screencapture disable-shadow -bool true
To make the changes take effect, logout and login, or restart SystemUIServer.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080629181121863