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.
[robg adds: This works, and I activated it with killall SystemUIServer in Terminal. To add the shadow effect back in, delete the newly-added pref: defaults delete com.apple.screencapture disable-shadow, then restart SystemUIServer again.]

