The browser in iTunes!
This is a useful feature in iTunes that never really got much fanfare! The search function is useful, but if you are not exactly sure of the spelling of what you are looking for, you're out of luck. This is especially true when your library is rather large. The browser will let you scroll through a list of artist, album or genre. If you have five thousand songs in your library, you might only have between five hundred and seven hundred artists. Scrolling through the list of artists might be much quicker. It can also work if you have visitors and you know they like a certain kind of music. You cannot simply type the "Genre" in the Search box. The browser will let you select the genre you want and it will reduce the list of songs accordingly. The only thing I find disappointing about the browser is that it doesn't work with coverflow. The view mode must be set to list. You can get the browser by choosing "Show browser" from the View menu or by hitting Command-B.