You can now do full text searches in iTunes. Doing so Search It will let iTunes playback the first found item that matches your search string. All fields (like artist name, album name, genre, etc.) are searched.
Eg. Searching for 'ace of spades' will (most likely) play the song 'Ace of Spades' by 'Motorhead'.
This feature is
RequirementsMac OS X 10.5.4 or later
*Previously available here