Not all of us like the new Leopard look although it's a great product. Here are some ways to make Leopard look more familiar to previous versions of Mac OS X. All tips require you to use the shell.

Remove the translucent Menu Bar effect

sudo defaults write /System/Library/LaunchDaemons/com.apple.WindowServer 'EnvironmentVariables' -dict 'CI_NO_BACKGROUND_IMAGE' 0.62

Switch the dock to 2D mode

defaults write com.apple.dock no-glass -boolean YES

Remove the default space desktop image

Even though you might have set another desktop background, the Login window still shows the space theme. To login look more neutral move the Image away.
sudo mv /System/Library/CoreServices/DefaultDesktop.jpg /System/Library/CoreServices/xDefaultDesktop.jpg