The dock got spiffy with the release of Leopard, but there have been mixed reviews of the new design. I’m mostly a fan of the new look, but I wish there was a better way of visually distinguishing between visible and hidden applications, like making hidden items darker or transparent. So, I rummaged around my preferences folder and came up with this command:
defaults write com.apple.dock showhidden -bool YES
Type it into Terminal, press return, and then enter the following:
Press return again, and quit and re-launch your applications. Go ahead and hide a few of them, and marvel that their icons are now darker and transparent than the icons for visible applications!
To revert to normal, issue the same commands, substituting NO for YES in the first.