There's been a good bit of debate about Leopard's new translucent menu bar. For me, it doesn't cause many issues. However, some of my coworkers despise it and, to be fair, I can see the arguments that many of the people who dislike it have: it doesn't add anything to the OS and actually makes it more difficult to read the text.
Well, here's a litle tweak that will set the menu bar back to a white background. In the terminal, you can use the following command to change the default appearance of the bar:
sudo defaults write /System/Library/LaunchDaemons/com.appledowServer 'EnvironmentVariables' -dict 'CI_NO_BACKGROUND_IMAGE' 1
Restart your Mac, and voila! White menu bar! Changed your mind? Set it back:
sudo defaults delete /System/Library/LaunchDaemons/com.apple.WindowServer 'EnvironmentVariables' -dict 'CI_NO_BACKGROUND_IMAGE'
Restart your Mac and your menu bar is back to being translucent.