With the advent of iTunes 7, Apple split what used to be a monolithic Library entry into several distinct libraries: Music, Movies, TV Shows, Podcasts, and Radio. While I think this makes sense in general, there are times when you’d like to be able to browse your entire collection of stuff without picking between libraries.
In versions of iTunes prior to 7.1, you could do this with a simple three-line AppleScript that returned the old monolithic Library behavior. However, Apple seems to have broken that solution in newer versions of iTunes. There is, however, another solution: use a simple Smart Playlist.
Create a new Smart Playlist with only one rule: Size - is greater than - 0MB. Make sure Live Updating is checked so that the Smart Playlist will update as you add new content to iTunes. Name your Smart Playlist whatever you like; I called mine Kitchen Sink, with an Option-Space at the front so it sorts to the top of the Playlists section. If you make sure the Kind column is visible in the main iTunes window, you can even sort your merged library by type of content. Since you’ll be looking at a Smart Playlist and not the Library itself, remember that to delete something from the Library (not just from the Playlist), you’ll need to use Option-Delete.
This isn’t a perfect replacement for the old all-in-one Library folder, but it’s a pretty decent substitute.